Waves, ound Light - WordPress.com · TE Demonstration Surfing Waves,p. 574g SE Connection to...

UNIT

T I M E L I N E

7

Waves, Sound, and LightWhen you hear the word waves, you probably think of waves in the ocean. But waves that you encounter every day have a much bigger effect on your life than do water waves! In this unit, you will learn about different types of waves, how waves behave and interact, and how sound energy and light energy travel in waves. This time-line shows some events and discoveries that have occurred throughout history as scientists have sought to learn more about the energy of waves.

570 Unit 7

Around1600

Italian astronomer and

physicist Galileo Galilei

attempts to calculate the

speed of light by using

lanterns and shutters. He

writes that the speed is

“extraordinarily rapid.”

1903The popularity of an early

movie called The Great

Train Robbery leads to

the establishment of

permanent movie theaters.

1960The first working laser

is demonstrated.

1971Hungarian physicist

Dennis Gabor wins the

Nobel Prize in physics for

his invention of holography,

the method used to make

holograms.

Waves, Sound, and Light 571

1905Physicist Albert

Einstein suggests

that light some-

times behaves as

a particle.

1704Sir Isaac Newton publishes his

book Optiks, which contains his

theories about light and color.

1801British scientist Thomas

Young is the first to

provide experimental

data showing that light

behaves as a wave.

1929American astronomer

Edwin Hubble uses the

Doppler effect of light

to determine that the

universe is expanding.

1983A “mouse” is first

used on personal

computers.

Scientists develop a thermoacoustic

refrigerator. The device is cooled

using high amplitude sound instead

of chemical refrigerants.

2002British pilot Andy

Green drives a

jet-powered car

at 341 m/s, when

he becomes the

first person to travel

faster than the speed

of sound on land.

1997

Anne Frank’s The

Diary of a Young

Girl is published.

The book is an

edited version of

the diary kept by a

Jewish teenager

while in hiding

during World War II.

1947

English trumpeter John

Shore invents the tuning

fork, an instrument that

produces a single-

frequency note.

1711

OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES

Compression guide:To shorten instructionbecause of time limitations,omit Section 3.

20 The Energy of WavesChapter Planning Guide

Chapter Opener

571A Chapter 20 • The Energy of Waves

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P81 Wave Motion* TR LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E28 Primary

Waves; Secondary Waves; SurfaceWaves*

TR P82 Comparing Longitudinal andTransverse Waves*

CRF SciLinks Activity*g SE Internet Activity, p. 577gCD Science Tutor

TE Demonstration Surfing Waves, p. 574g SE Connection to Astronomy Light Speed, p. 576g SE Science in Action Math, Social Studies, and Language

Arts Activities, pp. 596–597g

Section 1 The Nature of Waves• Describe how waves transfer energy without

transferring matter.• Distinguish between waves that require a medium

and waves that do not.• Explain the difference between transverse and

longitudinal waves.

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P83 Measuring Wavelengths* TR P83 Measuring Frequency*VID Lab Videos for Physical ScienceCD Science Tutor

TE Demonstration Pitch of a Rubber Band, p. 580g SE Quick Lab Springy Waves, p. 581g

CRF Datasheet for Quick Lab* TE Activity Constructing a Transverse Wave, p. 581b SE Skills Practice Lab Wave Energy and Speed,

p. 590gCRF Datasheet for Chapter Lab* SE Skills Practice Lab Wave Speed, Frequency, and

Wavelength, p. 740gCRF Datasheet for LabBook*

PACING • 90 min pp. 580–583Section 2 Properties of Waves• Identify and describe four wave properties.• Explain how frequency and wavelength are related to

the speed of a wave.

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P84 Constructive and Destructive

Interference*CD Science Tutor

TE Activity Wave Interactions, p. 584g TE Demonstration Refraction, p. 585g SE School-to-Home Activity What if Light Diffracted?,

p. 586g TE Connection Activity Real World, p. 586g TE Activity AM and FM Radio Waves, p. 586a TE Activity Creating Interference, p. 587b LB Whiz-Bang Demonstrations Pitch Forks*g LB Long-Term Projects & Research Ideas It’s a Whale of a

Wave*a

PACING • 45 min pp. 584–589Section 3 Wave Interactions• Describe reflection, refraction, diffraction, and

interference.• Compare destructive interference with constructive

interference.• Describe resonance, and give examples.

OSP Parent Letter ■

CD Student Edition on CD-ROM CD Guided Reading Audio CD ■

TR Chapter Starter Transparency*VID Brain Food Video Quiz

SE Start-up Activity, p. 573gpp. 572–579PACING • 90 min

CRF Vocabulary Activity*g SE Chapter Review, pp. 592–593g

CRF Chapter Review* ■g

CRF Chapter Tests A* ■g, B*a, C*s SE Standardized Test Preparation, pp. 594–595g

CRF Standardized Test Preparation*gCRF Performance-Based Assessment*gOSP Test Generator, Test Item Listing

CHAPTER REVIEW, ASSESSMENT, ANDSTANDARDIZED TEST PREPARATION

PACING • 90 min

Online and Technology Resources

Visit go.hrw.com foraccess to Holt OnlineLearning, or enter thekeyword HP7 Homefor a variety of freeonline resources.

This CD-ROM package includes:• Lab Materials QuickList Software• Holt Calendar Planner• Customizable Lesson Plans• Printable Worksheets

• ExamView® Test Generator• Interactive Teacher’s Edition• Holt PuzzlePro®

• Holt PowerPoint® Resources

STANDARDS CORRELATION SKILLS DEVELOPMENT RESOURCES SECTION REVIEW AND ASSESSMENT CORRELATIONS

Chapter 20 • Chapter Planning Guide 571B

CRF Directed Reading A* ■b, B *s IT Interactive Textbook* Struggling ReadersStruggling Readers

CRF Vocabulary and Section Summary* ■g

SE Reading Strategy Discussion, p. 574g TE Reading Strategy Prediction Guide, p. 575g TE Support for English Language Learners, p. 575 TE Inclusion Strategies, p. 577

SE Reading Checks, pp. 574, 576, 578g TE Reteaching, p. 578b TE Quiz, p. 578g TE Alternative Assessment, p. 578g SE Section Review,* p. 579 ■g

CRF Section Quiz* ■g

PS 3a

CRF Directed Reading A* ■b, B*s IT Interactive Textbook* Struggling ReadersStruggling Readers


SE Reading Strategy Mnemonics, p. 580g TE Support for English Language Learners, p. 581 TE Inclusion Strategies, p. 581 SE Math Focus Wave Calculations, p. 582g

CRF Reinforcement Worksheet Getting on the Same Frequency*b MS Math Skills for Science Dividing Whole Numbers with Long

Division*g

SE Reading Checks, pp. 581, 582g TE Reteaching, p. 582b TE Quiz, p. 582g TE Alternative Assessment, p. 582g SE Section Review,* p. 583 ■ g

CRF Section Quiz* ■g

UCP 3; SAI 1, 2; PS 3a; ChapterLab: SAI 1, 2; PS 3a; LabBook:SAI 1, 2

CRF Directed Reading A* ■b, B*s IT Interactive Textbook* Struggling ReadersStruggling Readers


SE Reading Strategy Reading Organizer, p. 584g TE Support for English Language Learners, p. 586

CRF Reinforcement Worksheet Makin’ Waves*bCRF Critical Thinking The Case of the Speeding Ticket*a

SE Reading Checks, pp. 585, 587, 588g TE Reteaching, p. 588b TE Quiz, p. 588g TE Alternative Assessment, p. 588g SE Section Review,* p. 589 ■ g

CRF Section Quiz* ■ g

UCP 3; PS 3a

National ScienceEducation Standards

SAI 1, 2; PS 3a

SE Pre-Reading Activity, p. 572gOSP Science Puzzlers, Twisters & Teasersg

CRF Chapter Resource File SS Science Skills Worksheets IT Interactive TextbookOSP One-Stop Planner MS Math Skills for Science Worksheets * Also on One-Stop Planner

SE Student Edition LB Lab Bank CD CD or CD-ROM ◆ Requires advance prepTE Teacher Edition TR Transparencies VID Classroom Video/DVD ■ Also available in Spanish

KEY

Maintained by the NationalScience Teachers Association.See Chapter Enrichment pagesthat follow for a complete listof topics.

www.scilinks.orgCheck out Current Sciencearticles and activities byvisiting the HRW Web siteat go.hrw.com. Just typein the keyword HP5CS20T.

• Lab Videos demonstratethe chapter lab.

• Brain Food Video Quizzeshelp students review thechapter material.

ClassroomVideos

Holt Lab GeneratorCD-ROM

Search for any lab by topic, standard,difficulty level, or time. Edit any labto fit your needs, or create your ownlabs. Use the Lab Materials QuickListsoftware to customize your labmaterials list.

• Guided Reading Audio CD(Also in Spanish)

• Interactive Explorations• Virtual Investigations• Visual Concepts• Science Tutor

ClassroomCD-ROMs

Planning ResourcesTEST ITEM LISTINGPARENT LETTERLESSON PLANS

Visual ResourcesBELLRINGER

TRANSPARENCIES TEACHING TRANSPARENCIESCHAPTER STARTER

TRANSPARENCY

TEST ITEM LISTING

Copyright © by Holt Rinehart and Winston All rights reserved

The World of ScienceMULTIPLE CHOICE

1. A limitation of models is thata. they are large enough to see.b. they do not act exactly like the things that they model.c. they are smaller than the things that they model.d. they model unfamiliar things.Answer: B Difficulty: I Section: 3 Objective: 2

2. The length 10 m is equal toa. 100 cm. c. 10,000 mm.b. 1,000 cm. d. Both (b) and (c)Answer: B Difficulty: I Section: 3 Objective: 2

3. To be valid, a hypothesis must bea. testable. c. made into a law.b. supported by evidence. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2 1

4. The statement "Sheila has a stain on her shirt" is an example of a(n)a. law. c. observation.b. hypothesis. d. prediction.Answer: B Difficulty: I Section: 3 Objective: 2

5. A hypothesis is often developed out ofa. observations. c. laws.b. experiments. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2

6. How many milliliters are in 3.5 kL?a. 3,500 mL c. 3,500, 000 mLb. 0.0035 mL d. 35,000 mLAnswer: B Difficulty: I Section: 3 Objective: 2

7. A map of Seattle is an example of aa. law. c. model.b. theory. d. unit.Answer: B Difficulty: I Section: 3 Objective: 2

8. A lab has the safety icons shown below. These icons mean that you should weara. only safety goggles. c. safety goggles and a lab apron.b. only a lab apron. d. safety goggles, a lab apron, and gloves.Answer: B Difficulty: I Section: 3 Objective: 2

9. The law of conservation of mass says the tot al mass before a chemical change isa. more than the total mass after the change.b. less than the total mass after the change.c. the same as the total mass after the change.d. not the same as the total mass after the change.Answer: B Difficulty: I Section: 3 Objective: 2

10. In which of the following areas might you find a geochemist at work?a. studying the chemistry of rocks c. studying fishesb. studying forestry d. studying the atmosphereAnswer: B Difficulty: I Section: 3 Objective: 2

TEACHER RESOURCE PAGE

Lesson Plan

Section: Waves

PacingRegular Schedule: with lab(s): 2 days without lab(s): 2 days

Block Schedule: with lab(s): 1 1/2 days without lab(s): 1 day

Objectives1. Relate the seven properties of life to a living organism.

2. Describe seven themes that can help you to organize what you learn aboutbiology.

3. Identify the tiny structures that make up all living organisms.

4. Differentiate between reproduction and heredity and between metabolismand homeostasis.

National Science Education Standards CoveredLSInter6: Cells have particular structures that underlie their functions.

LSMat1: Most cell functions involve chemical reactions.

LSBeh1:Cells store and use information to guide their functions.

UCP1:Cell functions are regulated.

SI1: Cells can differentiate and form complete multicellular organisms.

PS1: Species evolve over time.

ESS1: The great diversity of organisms is the result of more than 3.5 billion yearsof evolution.

ESS2: Natural selection and its evolutionary consequences provide a scientificexplanation for the fossil record of ancient life forms as well as for the strikingmolecular similarities observed among the diverse species of living organisms.

ST1: The millions of different species of plants, animals, and microorganismsthat live on Earth today are related by descent from common ancestors.

ST2: The energy for life primarily comes from the sun.

SPSP1: The complexity and organization of organisms accommodates the needfor obtaining, transforming, transporting, releasing, and eliminating the matterand energy used to sustain the organism.

SPSP6: As matter and energy flows through different levels of organization ofliving systems—cells, organs, communities—and between living systems and thephysical environment, chemical elements are recombined in different ways.

HNS1: Organisms have behavioral responses to internal changes and to externalstimuli.

This CD-ROM includes all of the resources shown here and the following time-saving tools:

• Lab Materials QuickList Software

• Customizable lesson plans

• Holt Calendar Planner

• The powerful ExamView ® Test Generator

Chapter Resources

Dear Parent,

Your son's or daughter's science class will soon begin exploring the chapter entitled “The

World of Physical Science.” In this chapter, students will learn about how the scientific

method applies to the world of physical science and the role of physical science in the

world. By the end of the chapter, students should demonstrate a clear understanding of the

chapter’s main ideas and be able to discuss the following topics:

1. physical science as the study of energy and matter (Section 1)

2. the role of physical science in the world around them (Section 1)

3. careers that rely on physical science (Section 1)

4. the steps used in the scientific method (Section 2)

5. examples of technology (Section 2)

6. how the scientific method is used to answer questions and solve problems (Section 2)

7. how our knowledge of science changes over time (Section 2)

8. how models represent real objects or systems (Section 3)

9. examples of different ways models are used in science (Section 3)

10. the importance of the International System of Units (Section 4)

11. the appropriate units to use for particular measurements (Section 4)

12. how area and density are derived quantities (Section 4)

Questions to Ask Along the Way

You can help your son or daughter learn about these topics by asking interesting questions

such as the following:

• What are some surprising careers that use physical science?

• What is a characteristic of a good hypothesis?

• When is it a good idea to use a model?

• Why do Americans measure things in terms of inches and yards instead of centimeters

and meters ?

TEACHING TRANSPARENCIES

Primary Waves; Secondary Waves; Surface WavesEarthquakes TEACHING TRANSPARENCY

Copyright © by Holt, Rinehart and Winston. All rights reserved.

P waves move rock back and forth, which squeezes and stretches the rock, as they travel through the rock.

Direction of wave travel

S waves shear rock side to side as they travel through the rock.


Surface waves move the ground much like ocean waves move water particles.


Measuring WavelengthsThe Energy of Waves TEACHING TRANSPARENCY


Wavelength can be measured from any two corre-sponding points that are adjacent on a wave.

Wavelength

Wavelength

Longitudinal wave

Transverse wave

Wavelength

Wavelength

Measuring Frequency

Frequency can be measured by counting how many waves pass by in a certain amount of time. Here, two waves went by in 10 s, so the frequency is2/10 s � 0.2 Hz.

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The Energy of Waves TEACHING TRANSPARENCY

Wave Motion

Wave motion

571C Chapter 20 • The Energy of Waves

20

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The Energy of Waves TEACHING TRANSPARENCY

Comparing Longitudinal and Transverse Waves

Troughs Crests

Tranverse wave

Rarefactions Compressions

Longitudinal wave

Pushing a spring back and forth creates a longitudinal wave, much the same way that shaking a rope up and down creates a transverse wave.

This ReallyHappened!On March 27, 1964, the most powerfulearthquake ever recorded on the NorthAmerican continent rocked Alaska. Thequake started on land near the city ofAnchorage, but the seismic waves spreadquickly in all directions, toppling build-ings and ripping up roads.

The earthquake created a series ofwaves called tsunamis (tsoo NAH mees)in the Gulf of Alaska. In the deep waterof the Gulf, the tsunamis were short andwidely separated. But as these wavesentered the shallow water surroundingKodiak Island, off the coast of Alaska,they became taller and closer together.One of the tsunamis rose to a height ofnearly 30 m! That’s as tall as an eight-story building.

The powerful tsunamis poundedeverything in their path. Eighty-one fish-ing boats were destroyed, and 86 oth-ers were damaged in the town of Kodiak.The destructive forces of the earthquakeand tsunamis killed 21 people andcaused $10 million in damage to Kodiak,making this the worst marine disaster inthe town’s 200-year history.

A tsunami is a dramatic example of theenergy of waves. But waves affect your lifein many common and less harmful ways.In fact, whenever you listen to music, talkwith your friends, or watch a sunrise, youare experiencing the energy of waves. Readon to find out more about waves and howthey affect your life every day.

The Energy of Waves CHAPTER STARTER


Anchorage

KodiakIsland

Seismic waves

Origin of the earthquake

The Energy of Waves BELLRINGER TRANSPARENCY


Section: The Nature of WavesWhat do you think of when you hear the word wave?

Write a brief description in your science journal

of what you think a wave is. Then write a shortparagraph describing a time you might haveexperienced waves.

Section: Properties of WavesDraw a longitudinal wave and a transverse wave inyour science journal. Label the parts of each wave.

CONCEPT MAPPING TRANSPARENCY

with or without a

which are used to calculate

transfercan be

wavelength

have

properties

such as

The Energy of Waves CONCEPT MAPPING TRANSPARENCY


Use the following terms to complete the concept map below:transverse, frequency, waves, longitudinal, wave speed, amplitude,energy, medium

Chapter: Earthquakes

SAMPLE SAMPLE SAMPLE

Meeting Individual Needs

Review and Assessments

Labs and Activities

DIRECTED READING A VOCABULARY ACTIVITY

STANDARDIZED TEST PREPARATIONCHAPTER TEST BCHAPTER REVIEWSECTION QUIZ

SCILINKS ACTIVITY

MARINE ECOSYSTEMS

Go to www.scilinks.com. To find links relatedto marine ecosystems, type in the keywordHL5490. Then, use the links to answer thefollowing questions about marine ecosys-tems.

1. What percentage of the Earth’s surface iscovered by water?

2. What percentage of the Earth’s water is found in the oceans?

3. What is the largest animal on Earth?

4. Describe an ocean animal.

Name Class Date

SciLinks ActivityActivity

Developed and maintained by theNational Science Teachers Association

Topic: Reproductive SystemIrregularitiesSciLinks code: HL5490


Name Class Date

Vocabulary ActivityActivity

Getting the Dirt on the SoilAfter you finish reading Chapter: [Unique Title], try this puzzle! Use the clues belowto unscramble the vocabulary words. Write your answer in the space provided.

1. the breakdown of rock intosmaller and smaller pieces:AWERIGNETH

2. layer of rock lying beneath soil:CROKDEB

3. type of crop that is plantedbetween harvests to reduce soilerosion: CROVE

4. action of rocks and sedimentscraping against each other andwearing away exposed surfaces:SABRONIA

5. a mixture of small mineral frag-ments and organic matter: LISO

6. rock that is a source of soil:PRATEN CORK

7. type of reaction that occurs whenoxygen combines with iron toform rust: oxidation

8. type of weathering caused byphysical means: CLEMANIACH

9. the chemical breakdown of rocksand minerals into new substances: CAMILCHETHEARIGWEN

10. layers of soil, to a geologist:SNORHIZO

11. the uppermost layer of soil:SPOTOIL

12. process in which rainwater car-ries dissolved substances fromthe uppermost layers of soil to thebottom layers: HELANCIG

13. small particles of decayed plantand animal material in soil:MUUSH

14. the process in which wind, water,or ice moves soil from one location to another: ROOSINE

15. the methods humans use to takecare of soil:OSIL VASETONRICON

LONG-TERM PROJECTS & RESEARCH IDEAS

REINFORCEMENT

WHIZ-BANGDEMONSTRATIONS

DATASHEETS FOR QUICKLABS

DATASHEETS FOR QUICK LABS

VOCABULARY AND SECTION SUMMARY


Section: EnergIn the space provided, write the letter of the description that best matches theterm or phrase.

______ 1. building molecules that can be used asan energy source. or breaking down moleculesin which energy is stored

______ 2. the process by which light energy is convertedto chemical energy

______ 3. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 4. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 5. an organism that consumes food to get energy

______ 6. the process of getting energy from food

In the space provided, write the letter of the term or phrase that best completeseach statement or best answers each question.

Name Class Date

Section QuizAssessment

a. photosynthesis

b. autotroph

c. heterotroph

d. cellular respiration

e. metabolism

f. cellular respiration

______ 7. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd. logs burning in a fire

______ 8. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______ 9. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______10. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd.

logs burning in a fire


Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

4. What is one question you will answer as you explore physical science?

5. Chemistry and physics are both fields of . Chemists

study the different forms of and how they interact.

and how it affects are

studied in physics.

Identify the field of physical science to which each of the following descriptionsbelongs by writing physics or chemistry in the space provided.

_______________________ 6. how a compass works

_______________________ 7. why water boils at 100°C

_______________________ 8. how chlorine and sodium combine to form table salt

_______________________ 9. why you move to the right when the car you are inturns left

Directed Reading A

Name Class Date

Skills Worksheet

DIRECTED READING B

Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

Directed Reading B

Name Class Date

Skills Worksheet

Section: UniqueVOCABULARY

In your own words, write a definition of the following term in the space provided.

1. scientific method

2. technology

3. observation

Name Class Date

Vocabulary & NotesSkills Worksheet

Name Class Date

ReinforcementSkills Worksheet

The Plane TruthComplete this worksheet after you finish reading the Section: [Unique SectionTitle]

You plan to enter a paper airplane contest sponsoredby Talkin’ Physical Science magazine. The personwhose airplane flies the farthest wins a lifetime sub-scription to the magazine! The week before the con-test, you watch an airplane landing at a nearbyairport. You notice that the wings of the airplane haveflaps, as shown in the illustration at right. The paperairplanes you’ve been testing do not have wing flaps.What question would you ask yourself based on these observations? Write yourquestion in the space below for “State the problem.” Then tell how you could usethe other steps in the scientific method to investigate the problem.

1. State the problem.

2. Form a hypothesis.

3. Test the hypothesis.

4. Analyze the results.

5. Draw conclusions.

Flaps


CRITICAL THINKING

A Solar Solution

Name Class Date

Critical Thinking Skills Worksheet

Joseph D. Burns

Inventors’ Advisory Consultants

Portland, OR 97201

Dear Mr. Burns,I’ve got this great idea for a new product called the BlissHeater. It’s a portable, solar-powered space heater. The heater’s design includes these features:•T

he heater will be as longas an adult’s arm and aswide as a

packing box.

•T

he heater will have aglass top set at an angleto catch the sun’s rays.

•T

he inside of the heaterwill be dark colored toabsorb solar heat.If you think my idea will work, I will make the Bliss

Heaters right away without wasting time and money on test-ing and making models. Please write back soon with youropinion.

SECTION REVIEW

Section: UniqueKEY TERMS

1. What do paleontologist study?

2. How does a trace fossil differ from petrified wood?

3. Define fossil.

UNDERSTANDING KEY IDEAS

Name Class Date

Section ReviewSkills Worksheet


[UniqueMULTIPLE CHOICE


______ 1. Surface currents are formed by a. the moon’s gravity. c. wind.b. the sun’s gravity. d. increased water density.

______ 2. When waves come near the shore, a. they speed up. c. their wavelength increases.b. they maintain their speed. d. their wave height increases.

______ 3. Longshore currents transport sediment a . out to the open ocean. c. only during low tide.b. along the shore. d. only during high tide.

______ 4. Which of the following does NOT control surface currents?a. global wind c. Coriolis effectb. tides d. continental deflections

______ 5. Whitecaps break a. in the surf. c. in the open ocean.b. in the breaker zone. d. as their wavelength increases.

______ 6. Most ocean waves are formed by a . earthquakes. c. landsides.b. wind. d. impacts by cosmic bodies.

______ 7. Which factor controls surface currents? a. global winds c. continental deflectionb. the Coriolis effect d. all of the above

______ 8. Streamlike movments of ocean water far below the surface arecalleda. jet currents c. surface currents.b. Coriolis currents. d. deep currents.

______ 9. When the sunlit part of the moon that can be seen from Earthgrows larger, it is a. waxing. c. in the new moon phase.b. waning. d. in the full moon phase.

______10. The Milky Way is thought to be a. an elliptical galaxy. c. a spiral galaxy.

Name Class Date

Chapter Test BAssessment


READING

Read the passages below. Then, read each question that follows the passage.Decide which is the best answer to each question.

Passage 1 adventurous summer camp in the world. Billy can’twait to head for the outdoors. Billy checked the recommendedsupply list: light, summer clothes; sunscreen; rain gear; heavy,down-filled jacket; ski mask; and thick gloves. Wait a minute! Billythought he was traveling to only one destination, so why does heneed to bring such a wide variety of clothes? On further investiga-tion, Billy learns that the brochure advertises the opportunity to“climb the biomes of the world in just three days.” The destinationis Africa’s tallest mountain, Kilimanjaro.

______ 1. The word destination in this passage means A camp B vacation.C place. D mountain.

______ 2. Which of the following is a FACT in the passage? F People ski on Kilimanjaro.G Kilimanjaro is Africa’s tallest mountain.H It rains a lot on Kilimanjaro.J The summers are cold on Kilimanjaro.

______ 3. Billy wondered if the camp was advertising only one destination afterhe read the brochure, which said thatA the camp was the most adventurous summer camp in the world. B he would need light, summer clothes and sunscreen.C he would need light, summer clothes and a heavy, down-filled

jacket.D the summers are cold on Kilimanjaro.

Name Class Date

Standardized Test PreparationAssessment

PERFORMANCE-BASEDASSESSMENT

OBJECTIVEDetermine which factors cause some sugar shapes to break down faster than others.

KNOW THE SCORE!As you work through the activity, keep in mind that you will be earning a gradefor the following:

• how you form and test the hypothesis (30%)

• the quality of your analysis (40%)

• the clarity of your conclusions (30%)

ASK A QUESTIONSWhy do some sugar shapes erode more rapidly than others?

MATERIALS AND EQUIPMENT

Name Class Date

Performanced-Based AssessmentAssessment SKILL BUILDER

Using Scientific Methods

• 1 regular sugar cube • 90 mL of waterCopyright © by Holt, Rinehart and Winston. All rights reserved.

USING VOCABULARY

1. Define biome in your own words.

2. Describe the characteristics of a savanna and a desert.

3. Identify the relationship between tundra and permafrost.

4. Compare the open-water zone and the deep-water zone.

5. Use each of the following terms in an original sentence: plankton, littoralzone, and estuary.

6. Describe how marshes and swamps differ.

Name Class Date

Chapter ReviewSkills Worksheet

CHAPTER TEST A






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test AAssessment

CHAPTER TEST C






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test CAssessment

Chapter 20 • Chapter Resources 571D

Trans Title

SCIENCE PUZZLERS, TWISTERS & TEASERS

Wave Rhyme Time1. These clues describe two words that rhyme. In each example, one

of the words is a term from the chapter. Write both words in thespace provided.a. Better than the rest, the highest point of a transverse wave.

b. A section where the particles are less crowded than normal andyet maintain a good grip.

Saxophones Don’t Belong in Rock ’n Roll Bands2. Ted plays the saxophone and enjoys rock ‘n roll. He joined some

bands so he could perform on stage. But, things didn’t work out.Tell what problems Ted encountered in each band.a. In his first band, Ted played the baritone saxophone. However,

when they played together, the crests of Ted’s waves overlappedh h f S h b i ’ Th l

Name _______________________________________________ Date ________________ Class______________

SCIENCE PUZZLERS, TWISTERS & TEASERS20

The Energy of Waves

CHAPTER

On June 15, 1896, the fishermen working 20 km off the coast of Honshu, Japan’smain island, didn’t even notice the wave gently passing under their boat. However,

when they returned later that day to the port city ofSanriku, they were bewildered by what they saw.

The wave that passed under their boat had been atsunami, a huge wave caused by an underwaterdisturbance such as an earthquake or volcano.It had grown taller as it neared the shore,killing 28,000 people and destroying 200 kmof coastline.

Tsunami Trouble1. Tsunamis travel far across the ocean without losing much

energy. They can move at 700 km/h, and reach a height of 30 m on shore! Find out more about the worst tsunamidisasters in history. What measures are being taken todayto protect communities at risk? Write a fictional first-person account of a tsunami disaster based on yourresearch.

Other Research Ideas2. Did you know that waves can heal? Ultrasound technol-

ogy, which uses sound waves with frequencies of 20,000 Hzand above, has a number of medical uses. For example,physicians use ultrasound waves to “shatter” kidney stonesand some types of tumors without surgery. Find out moreabout how ultrasound works and how it is used in othermedical situations. Prepare a poster to display your findings.

3. Can noise be harmful to your health? Unfortunately, yes.What health problems besides hearing loss can be causedby too much noise? Research the Noise Control Act and learn about the measures that the EnvironmentalProtection Agency uses to control noise pollution. Presentyour findings in the form of a magazine article.

Long-Term Project Idea4. What do a piano tuner, a geologist, an air traffic controller,

and an EKG technician have in common? They all usetheir knowledge of waves to help them every day at work.Videotape an interview with a member of one of theseprofessions. If possible, ask the person to demonstratewhat he or she does at work. To prepare for your inter-view, research the skills involved in one of these profes-sions and write a list of questions. Share your interviewtape with your class.

Name ___________________________________________________ Date _________________ Class _____________

PROJECT

STUDENT WORKSHEET70

It’s a Whale of a Wave

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INTERNETKEYWORDS

Noise Control Act

noise pollution

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TEACHER-LED DEMONSTRATION

DEMO

60

Pitch ForksPurpose

Students observe the nature of waves.

Time Required

10–15 minutes

Advance Preparation

To be sure that every student is able to seethe activity, it may be necessary to set sev-eral beakers around the classroom. Thiswill allow smaller groups to watch as youperform this demonstration.

What to Do

1. Strike the three tuning forks. As you aredoing this, ask students to listen forthree distinct tones.

2. Ask students if they can imagine whatdifferent sound waves look like as theytravel through air.

3. Fill the beaker with cold water.

4. Strike each of the three tuning forks.Ask students how many distinct tonesthey hear. (Each fork produces a differenttone, so students should hear three distincttones.)

5. Strike one of the tuning forks, andtouch the prongs lightly to the surfaceof the water. Ask students to observethe waves created on the surface of thewater. Repeat this with the other twoforks.

Explanation

Each fork produces a different tone andcreates waves of different wavelengths inthe water. Sound travels in air in the sameway that ripples move through water. Asthe prongs of the tuning fork vibrate, theypush on the air molecules around them.This energy is passed from one moleculeto the next. As sound waves movethrough the air, air molecules are alter-nately compressed and spread apart, muchlike a wave moving in water. Both the wa-ter and sound move in longitudinal waves.

As students listened to the three tuningforks, they should have noticed that eachfork emitted a tone at a different pitch.The pitch of a sound is related to its fre-quency, or the number of vibrations in agiven amount of time. A sound with ahigher pitch is a wave with a higher fre-quency. Therefore, the high-pitched tun-ing fork created waves in the water withthe highest frequency. The low-pitchedtuning fork produced fewer waves in thesame amount of time.

MATERIALS

• 3 tuning forks that produce different tones• beaker• tap water

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

Kenneth HornFallstone Middle School

Fallstone, Maryland

For a preview of available worksheets covering math and science skills, see pages T26–T33. All of these resources are also on the One-Stop Planner®.

Copyright © by Holt, Rinehart and Winston. All rights reserved.Copyright © by Holt, Rinehart and Winston. All rights reserved.


Name Class Date

Reaction to StressQuick Lab DATASHEET FOR QUICK LAB

BackgroundThe graph below illustrates changes that occur in the membrane potential of aneuron during an action potential. Use the graph to answer the followingquestions. Refer to Figure 3 as needed.

Analysis1. Determine about how long an action potential lasts.

2. State whether voltage-gated sodium, chanels are open or closed at point A.

3. State whether voltage-gated potassium channels are open or closed atpoint B.

4. Critical Thinking Recognizing Relationships What causes the menberneotential to become less negative at point A?

5. Critical Thinking Recognizing Relationships What causes the membranepotential to become more negative at point B?


Answer here.

Answer here.

Answer here.

Answer here.

Answer here.

Using Scientific Methods

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SPECIAL NEEDS

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DATASHEETS FORCHAPTER LABS

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

RATINGTeacher Prep–3Student Set-Up–2Concept Level–2Clean Up–2

MATERIALS

The materials listed on the student page are enough for a group of 4–5 students.Large, dried beans of any kind will work well in this exercise.

SAFETY CAUTION

Remind students to review all safety cautions and icons before beginning this labactivity.

Using Scientific MethodsSkills Practice Lab DATASHEET FOR CHAPTER LAB


1 2 3 4Easy Hard

Jason MarshMontevideo High

and Country School

SAMPLE

DATASHEETS FORLABBOOK

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

Does It All Add Up?Skills Practice Lab DATASHEET FOR LABBOOK LAB


Jason MarshMontevideo High

SAMPLE

Chapter Enrichment

This Chapter Enrichment provides relevant and

interesting information to expand and enhance

your presentation of the chapter material.

The Nature of WavesTsunamis• What many people call tidal waves are not caused by the

tides. They are usually caused by undersea earthquakes,volcanic eruptions, landslides, or violent windstormsthat occur over the open sea. A large wave produced byany of these phenomena is called a tsunami.

• Tsunamis often begin as a series of small waves nolarger than 1 m high but traveling at great speed(188 m/s) over deep water. In deep water, a tsunamimay not even be seen. However, when the depth ofthe water becomes less than the height of the wave,the wave builds into a wall of water that can reach aheight of 30 m or higher.

Mechanical Waves• Some scientists call a wave “a wiggle in time and

space.” Mechanical waves are periodic disturbancesthat pass through matter. As a wave passes throughmatter, the material’s particles vibrate about their restpositions, and only the energy moves through. Someof the wave’s energy is used to do work on the parti-cles. Mechanical waves eventually die out as theirenergy is dissipated.

Electromagnetic Waves• An electromagnetic wave is a transverse wave com-

prising oscillating electric and magnetic fields atright angles to each other. Electromagnetic waves,like mechanical waves, are described in terms ofwavelength and frequency. Types of electromagneticwaves (from longest wavelength to shortest) includeradio waves, microwaves, infrared waves, visible light,ultra-violet light, X rays, and gamma rays.

Properties of WavesWaves• A wave is produced by a vibrating object. For example,

music is produced by vibrating strings or by vibratingcolumns of air. Electromagnetic waves can be pro-duced by vibrating electrons.

• The frequency of the wave is equal to the frequency ofthe vibrating object. The square of the amplitude ofthe wave is proportional to the energy used to producethe wave.

• The speed of a wave depends on the medium throughwhich the wave travels. For mechanical waves, thedensity, elasticity, and temperature of the mediumaffect the speed. A mechanical wave’s speed increaseswith elasticity and decreases with density. For exam-ple, the speed of sound at 0°C is 331.5 m/s in air and5,200 m/s in steel.

Is That a Fact!◆ Heinrich Hertz (1857–1894) was a German physicist.

The unit for describing frequency is named in hishonor. Hertz’s goal was to prove Maxwell’s theoryof electromagnetic radiation. While Hertz wasperforming his experiments, he discovered radiowaves. This discovery led to the developmentof radio, radar, and television.

Longitudinal Waves and Wavelength• Longitudinal waves do not have high and low points,

but they do have regions of high pressure (compres-sions) and regions of low pressure (rarefactions).

571E Chapter 20 • The Energy of Waves

20

Topic: Nature of WavesSciLinks code: HSM1017

Topic: Types of WavesSciLinks code: HSM1574

Topic: Properties of WavesSciLinks code: HSM1236

Topic: Interactions of WavesSciLinks code: HSM0805

Visit www.scilinks.org and enter the SciLinks code formore information about the topic listed.


SciLinks is maintained by the National Science Teachers Associationto provide you and your students with interesting, up-to-date links thatwill enrich your classroom presentation of the chapter.

• Sound waves are an example of longitudinal waves.When you strike a tuning fork, the prongs vibrateback and forth. Like a drum, the tuning fork sendsout compressions when the prongs vibrate out andrarefactions when the prongs vibrate back. The com-pressions of the sound waves correspond to crests.Rarefactions of sound waves correspond to troughs.Therefore, the wavelength of a sound wave is thedistance between adjacent compressions or adjacentexpansions.

Is That a Fact!◆ If you are listening to your favorite radio station,

which has a frequency of 96.1 MHz (96,100,000 Hz),the electrons in the radio antenna are vibrating at thesame frequency—96,100,000 vibrations/second.

Wave InteractionsChristiaan Huygens• Christiaan Huygens (1629–1695)

was a Dutch mathematician,astronomer, and physicist.His life overlapped thoseof Galileo (1564–1642) andNewton (1642–1727). Manyhistorians believe that Huygens’scontributions to science weremuch broader than those ofeither Newton or Galileo.

• Huygens invented the pendulum clock and developedthe first wave theory. Huygens’s theory states that anypoint on a wave can be a source of a new disturbance.

Lasers• In 1960, T. H. Maiman and others built the first suc-

cessful laser. They used a large ruby crystal doped withchromium-ion impurities as the source of light. Theelectrons of the chromium ions were excited by a spe-cial flash lamp. The excited ions dropped to a lowerenergy level almost immediately and emitted photonsof a single wavelength.

Is That a Fact!◆ The word refraction comes from the Latin prefix

re-, meaning “back,” and frangere, meaning“to break.”

For background information about teaching strategies and

issues, refer to the Professional Reference for Teachers.

Chapter 20 • Chapter Enrichment 571F

Standards Correlations

OverviewTell students that this chapterwill help them learn about thenature of waves. The chapterdiscusses the characteristicsand properties of waves andthe different kinds of waveinteractions.

Assessing PriorKnowledgeStudents should be familiarwith the following topics:

• matter

• motion

• energy

IdentifyingMisconceptionsThe motion of the medium (i.e.,water) is frequently confusedwith the motion of the waveitself. Students also confuse theindependent aspects of waves,such as amplitude, frequency,and velocity. A common belief isthat a rapid oscillation ensures alarge amplitude and fastvelocity. Students may intuitthat wave collisions will resultin the permanent cancellationof both waves as if they weremechanical objects.

National Science Education Standards

The following codes indicate the National Science EducationStandards that correlate to this chapter. The full text of thestandards is at the front of the book.

Chapter OpenerSAI 1, 2; PS 3a

Section 1 The Nature of WavesPS 3a

Section 2 Properties of WavesUCP 3; SAI 1, 2; PS 3a; LabBook: SAI 1, 2

Section 3 Wave InteractionsUCP 3; PS 3a

Chapter LabSAI 1, 2; PS 3a

Chapter ReviewPS 3a

Science in ActionST 1, 2; HNS 3; PS 3a

572 Chapter 20 • The Energy of Waves

20

PRE-READINGPRE-READING

The Energy of Waves

About the

A surfer takes advantage of a wave’s energyto catch an exciting ride. The ocean wave thatthis surfer is riding is just one type of wave.You are probably familiar with water waves.But did you know that light, sound, and evenearthquakes are waves? From music to televi-sion, waves play an important role in your lifeevery day.

Three-Panel Flip ChartBefore you read the chapter,create the FoldNote entitled

“Three-Panel Flip Chart” described in theStudy Skills section of the Appendix.Label the flaps of the three-panel flipchart with “The nature of waves,”“Properties of waves,” and “Waveinteractions.” As you read the chapter,write informationyou learn abouteach categoryunder theappropriate flap.

SECTION

Waves transfer energy, havedescribable properties, andinteract in predictable ways.

20

1 The Nature of Waves . . . . . . . . 574

2 Properties of Waves . . . . . . . . 580

3 Wave Interactions . . . . . . . . . . 584

START-UPEnergetic WavesIn this activity, you will observe the movement of a wave. Then, you will determine the source of the wave’s energy.

Procedure1. Tie one end of a piece of rope to the back of

a chair.

2. Hold the other end in one hand, and stand away from the chair so that the rope is almost straight but is not pulled tight.

3. Move the rope up and down quickly to create a wave. Repeat this step several times. Record your observations.

Analysis1. In which direction does the wave move?

2. How does the movement of the rope compare with the movement of the wave?

3. Where does the energy of the wave come from?

START-UPSTART-UP vvM A T E R I A L S

FOR EACH GROUP• chair• rope, 1–2 meters

Answers

1. The wave moves from one end of the rope to the other.

2. Each piece of rope moves up and down, that is, in a direction dif-ferent from the wave. (If students have difficulty observing this, tie a piece of yarn to the rope, and have students watch only the yarn while waves are being made. The yarn will clearly move only up and down.)

3. The energy of the wave comes from shaking the rope. When students stop shaking the rope, the wave eventually stops moving.

This ReallyHappened!On March 27, 1964, the most powerfulearthquake ever recorded on the NorthAmerican continent rocked Alaska. Thequake started on land near the city ofAnchorage, but the seismic waves spreadquickly in all directions, toppling build-ings and ripping up roads.

The earthquake created a series ofwaves called tsunamis (tsoo NAH mees)in the Gulf of Alaska. In the deep waterof the Gulf, the tsunamis were short andwidely separated. But as these wavesentered the shallow water surroundingKodiak Island, off the coast of Alaska,they became taller and closer together.One of the tsunamis rose to a height ofnearly 30 m! That’s as tall as an eight-story building.

The powerful tsunamis poundedeverything in their path. Eighty-one fish-ing boats were destroyed, and 86 oth-ers were damaged in the town of Kodiak.The destructive forces of the earthquakeand tsunamis killed 21 people andcaused $10 million in damage to Kodiak,making this the worst marine disaster inthe town’s 200-year history.

A tsunami is a dramatic example of theenergy of waves. But waves affect your lifein many common and less harmful ways.In fact, whenever you listen to music, talkwith your friends, or watch a sunrise, youare experiencing the energy of waves. Readon to find out more about waves and howthey affect your life every day.

The Energy of Waves CHAPTER STARTER


Anchorage

KodiakIsland

Seismic waves

Origin of the earthquake

Chapter Starter TransparencyUse this transparency to help students begin thinking about waves and wave energy.

CHAPTER RESOURCESTechnology

Transparencies • Chapter Starter Transparency

Student Edition on CD-ROM

Guided Reading Audio CD • English or Spanish

Classroom Videos • Brain Food Video Quiz

Workbooks

Science Puzzlers, Twisters & Teasers • The Energy of Waves g

READINGSKILLS

Chapter 20 • The Energy of Waves 573

READING STRATEGY

1 The Nature of WavesImagine that your family has just returned home from a day at the beach. You had fun playing in the ocean under a hot sun. You put some cold pizza in the microwave for dinner, and you turn on the radio. Just then, the phone rings. It’s your friend calling to ask about homework.

In the events described above, how many different waves werepresent? Believe it or not, there were at least five! Can you namethem? Here’s a hint: A wavewave is any disturbance that transmitsenergy through matter or empty space. Okay, here are theanswers: water waves in the ocean; light waves from the sun;microwaves inside the microwave oven; radio waves transmit-ted to the radio; and sound waves from the radio, telephone,and voices. Don’t worry if you didn’t get very many. You willbe able to name them all after you read this section.

✓✓Reading Check What do all waves have in common? (See the

Appendix for answers to Reading Checks.)

Wave EnergyEnergy can be carried away from its source by a wave. You canobserve an example of a wave if you drop a rock in a pond.Waves from the rock’s splash carry energy away from the splash.However, the material through which the wave travels doesnot move with the energy. Look at Figure 1. Can you movea leaf on a pond if you are standing on the shore? You canmake the leaf bob up and down by making waves that carryenough energy through the water. But you would not makethe leaf move in the same direction as the wave.

wavewave a periodic disturbance in a solid, liquid, or gas as energy is transmitted through a medium

Figure 1 Waves on a pond move toward the shore, but the water and the leaf floating on the surface only bob up and down.

Wave motion

What You Will Learn

Describe how waves transfer energywithout transferring matter.Distinguish between waves thatrequire a medium and waves thatdo not.Explain the difference betweentransverse and longitudinal waves.

Vocabularywave transverse wavemedium longitudinal wave

Discussion Read this section silently.Write down questions that you haveabout this section. Discuss yourquestions in a small group.

OverviewIn this section, students learnthat waves are a means oftransmitting energy. Studentslearn about different types ofwaves and their properties.

BellringerHave students answer thefollowing question:

What do you think of whenyou hear the word wave?Write a brief description ofwhat you think a wave is.Then, write a short paragraphdescribing a time you mighthave experienced waves.

Discuss with students some oftheir answers.

Demonstration ---------------gSurfing Waves Show studentsa video or photographs of peo-ple surfing the giant waves ofCalifornia, Hawaii, South Africa,or Australia. Explain that thissection introduces basic con-cepts about waves but that thewaves that “break” as surfersride them are not covered—scientists still do not fullyunderstand why waves break.Studying waves around theworld might make a fun career!l Visual Answer to Reading Check

All waves are disturbances that transmit energy.

1

CHAPTER RESOURCES

Chapter Resource File

CRF • Lesson Plan• Directed Reading Ab• Directed Reading Bs

Technology

Transparencies• Bellringer• P81 Wave Motion• LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E28 Primary Waves;

Secondary Waves; Surface Waves

Workbooks

Interactive Textbook Struggling Readers Struggling Readers


Waves and WorkAs a wave travels, it does work on everything in its path. Thewaves in a pond do work on the water to make it move upand down. The waves also do work on anything floating onthe water’s surface. For example, boats and ducks bob up anddown with waves. The fact that these objects move tells youthat the waves are transferring energy.

Energy Transfer Through a MediumMost waves transfer energy by the vibration of particles in amedium. A medium is a substance through which a wave cantravel. A medium can be a solid, a liquid, or a gas. The pluralof medium is media.

When a particle vibrates (moves back and forth, as inFigure 2), it can pass its energy to a particle next to it. Thesecond particle will vibrate like the first particle does. In thisway, energy is transmitted through a medium.

Sound waves need a medium. Sound energy travels by thevibration of particles in liquids, solids, and gases. If there areno particles to vibrate, no sound is possible. If you put analarm clock inside a jar and remove all the air from the jar tocreate a vacuum, you will not be able to hear the alarm.

Other waves that need a medium include ocean waves,which move through water, and waves that are carried onguitar and cello strings when they vibrate. Waves that need amedium are called mechanical waves. Figure 3 shows the effectof a mechanical wave in Earth’s crust: an earthquake.

medium a physical environmentin which phenomena occur

Figure 2 A vibration is onecomplete back-and-forthmotion of an object.

Figure 3 Earthquakes causeseismic waves to travel throughEarth’s crust. The energy theycarry can be very destructive toanything on the ground.

READINGSTRATEGY ------------------ GENERAL

Prediction Guide Beforestudents read this section, askthem whether the followingstatements are true or false:

• Light waves are mechanicalwaves because they must travelin a medium. (false)

• In space, no one can hear anexplosion. (true)

• Water waves are a combinationof longitudinal and transversewaves. (true)l Logical

Is That a Fact!Underwater Earthquakes Most earth-quakes that take place on Earth happenunderwater! Very large underwaterearthquakes can cause huge wavescalled tsunamis that can be verydestructive to anything on the shore.

MISCONCEPTIONALERT

Sounds in a Vacuum Students maybelieve that sounds can be heard in avacuum. In many science-fiction movies,explosions and other sounds are heardin outer space. This is scientificallyinaccurate.

SUPPORT FOR

English LanguageLearnersScientific Vocabulary Manyterms in this section havescientific definitions. Somewords students will havelearned before in a differentcontext, and others will beentirely new. Encourage stu-dents to read each paragraphcarefully and try to discoverthe meaning of unknownwords through context. Havethem keep a running list ofwords they do not know.When they have finishedreading, ask partners to com-pare their lists of unknownwords and share the meaningof any words they know thatappear on a partner’s list. Ifany undefined words remainon the lists, have studentslook them up in a dictionaryand copy the definition intheir science journals. Unde-fined words may include: na-ture, disturbance, bob, medium,vacuum, repeated, crests andtroughs, boundary. l Verbal/Interpersonal

Section 1 • The Nature of Waves 575

Light Speed Light waves from stars and galaxies travel great distances that are best expressed in light-years. A light-year is the distance a ray of light can travel in one year. Some of the light waves from these stars have traveled billions of light-years before reaching Earth. Do the following calculation in your science jour-nal: If light travels at a speed of 300,000,000 m/s, what distance is a light-minute? (Hint: There are 60 s in a minute.)

Energy Transfer Without a MediumSome waves can transfer energy without going through a medium. Visible light is one example. Other examples include microwaves made by microwave ovens, TV and radio signals, and X rays used by dentists and doctors. These waves are electromagnetic waves.

Although electromagnetic waves do not need a medium, they can go through matter, such as air, water, and glass. The energy that reaches Earth from the sun comes through electromagnetic waves, which go through space. As shown in Figure 4, you can see light from stars because electromagnetic waves travel through space to Earth. Light is an electromagnetic wave that your eyes can see.

✓Reading Check How do electromagnetic waves differ from mechanical waves?

Figure 4 Light waves are electromagnetic waves, which do not need a medium. Light waves from the Crab nebula, shown here, travel through the vacuum of space billions of miles to Earth, where they can be detected with a telescope.

CONNECTION toCONNECTION toReal World --------------------------------------------g

Microwave Ovens Microwaveovens use electromagnetic waves to heat food. When the micro-wave energy penetrates a food item in a microwave oven, some of the energy from the waves causes water molecules to vibrate rapidly. The vibrating molecules are converting kinetic energy to thermal energy, which warms the rest of the particles in the food by conduction.

Electromagnetic RadiationAlbert Einstein, perhaps the world’s most famous scientist, proposed that electromagnetic radiation could be viewed as a stream of particles, rather than as a wave of energy. He called these particles photons. In fact, Einstein proposed that energy is equivalent to mass and that photons effectively have mass. Experiments have proved that Einstein was right.

Answer to Reading Check

Electromagnetic waves do not require a medium.


Crests

Troughs

Types of WavesAll waves transfer energy by repeated vibrations. However,waves can differ in many ways. Waves can be classified basedon the direction in which the particles of the medium vibratecompared with the direction in which the waves move. Thetwo main types of waves are transverse waves and longitudinal(LAHN juh TOOD’n uhl) waves. Sometimes, a transverse waveand a longitudinal wave can combine to form another kindof wave called a surface wave.

Transverse WavesWaves in which the particles vibrate in an up-and-downmotion are called transverse waves. Transverse means “movingacross.” The particles in this kind of wave move across, orperpendicularly to, the direction that the wave is going. Tobe perpendicular means to be “at right angles.”

A wave moving on a rope is an example of a transversewave. In Figure 5, you can see that the points along the ropevibrate perpendicularly to the direction the wave is going.The highest point of a transverse wave is called a crest,and the lowest point between each crest is called a trough(TRAWF). Although electromagnetic waves do not travel byvibrating particles in a medium, all electromagnetic waves areconsidered transverse waves. The reason is that the waves aremade of vibrations that are perpendicular to the direction ofmotion.

transverse wave a wave in whichthe particles of the medium moveperpendicularly to the direction thewave is traveling

A wave on a rope is a transverse wavebecause the particles of the medium vibrateperpendicularly to the direction the wave moves.

The wave travels to the right.

The points alongthe rope vibrateup and down.

Figure 5 Motion of a Transverse Wave

For another activity relatedto this chapter, go togo.hrw.com and type in thekeyword HP5WAVW.

CulturalAwarenessCulturalAwareness g

Women in Science HerthaMarks Ayrton (1854–1923)was a British physicist. Herfirst accomplishment wasinventing and patenting theline divider, a tool for archi-tects. Her primary interestswere the electric arc and cer-tain sand ripples found onbeaches. The ripples form asa result of wave action alongthe shore. The electric arcwas widely used for lighting.Ayrton was the first womanto read a research paper tothe Royal Society. AlthoughAyrton could not become amember of the societybecause she was a woman,she was awarded the HughesMedal for her research on theelectric arc and sand ripples.Have interested studentswrite a research paper aboutAyrton’s life and research.l Logical

StrategiesStrategiesINCLUSIONINCLUSION

• Visually Impaired• Developmentally Delayed• Learning DisabledMake the activity shown inFigure 5 come alive for allthe students in these twoways:

1. Prepare a rope as shown,tie it to a doorknob, andcreate the wave as shown.

2. Using squirt glue or fabricpaint, draw the wavyrope and the points on apiece of thick cardboard.When the glue or paintdries, let students whoare visually impaired feelthe raised path so thatthey can understand theconcepts.

l Kinesthetic ee

MISCONCEPTIONALERT

Transverse Waves In this chapter,transverse waves are often representedas moving up and down. However, stu-dents should understand that not alltransverse waves move in a verticalplane. A transverse wave is any wavein which the particles of the mediumvibrate perpendicularly to the directionthe wave moves.


Longitudinal WavesIn a longitudinal wave,longitudinal wave, the particles of the medium vibrateback and forth along the path that the wave moves. You canmake a longitudinal wave on a spring. When you push onthe end of the spring, the coils of the spring crowd together.A part of a longitudinal wave where the particles are crowdedtogether is called a compression. When you pull back on theend of the spring, the coils are pulled apart. A part where theparticles are spread apart is a rarefaction (RER uh FAK shuhn).Compressions and rarefactions are like the crests and troughsof a transverse wave, as shown in Figure 6.

Sound WavesA sound wave is an example of a longitudinal wave. Soundwaves travel by compressions and rarefactions of air particles.Figure 7 shows how a vibrating drum forms compressions andrarefactions in the air around it.

✓✓Reading Check What kind of wave is a sound wave?

longitudinal wavelongitudinal wave a wave in which the particles of the medium vibrate parallel to the direction of wave motion

Figure 7 Sound energy is carried away from a drum by a longitudinal wave through the air.

When the drumhead moves out after being hit, a compression is created in the air particles.

When the drumhead moves back in, a rarefaction is created.

Figure 6 Comparing Longitudinal and Transverse Waves

Troughs Crests

Transverse wave

Rarefactions Compressions

Longitudinal wave

Pushing a spring back and forth creates a longitudinal wave, much the same way that shaking a rope up and down creates a transverse wave.


Transparencies• P82 Comparing Longitudinal and

Transverse Waves

Reteaching -------------------------------------bWave Examples Have studentsbrainstorm as many examples ofwaves as they can think of. Foreach example, have them statewhat makes it a wave and whetherit is a transverse, longitudinal, orsurface wave. l Logical

Quiz ---------------------------------------------------------------------g

1. A wave is a disturbance thattravels through _____ or _____.(space, matter)

2. A wave carries _____. (energy)

3. Waves that require amedium are called _____waves. (mechanical)

4. Waves that do not requirea medium are called _____waves. (electromagnetic)

5. Waves produced by a combi-nation of longitudinal andtransverse waves are called_____ waves. (surface)

AlternativeAssessment ---------------------------g

PORTFOLIO

Models of WavesProvide students with

markers, construction paper,yarn, glue, and scissors. Havestudents use these materials toillustrate the following threewave types: longitudinal, trans-verse, and surface. Studentsshould label their waves and themedium (if any) through whichthe wave is moving and shouldindicate compressions, rarefac-tions, crests, and troughs.l Kinesthetic Answer to Reading Check

A sound wave is a longitudinal wave.


For a variety of links related to this chapter, go to www.scilinks.org

SummarySummary

Wave Motion

Review

Combinations of WavesWhen waves form at or near the boundary between two media, a transverse wave and a longitudinal wave can combine to form a surface wave. An example is shown in Figure 8. Surface waves look like transverse waves, but the particles of the medium in a surface wave move in circles rather than up and down. The particles move forward at the crest of each wave and move backward at the trough.

Figure 8 Ocean waves are surface waves. A floating bottle shows the circular motion of particles in a surface wave.

• A wave is a disturbance that transmits energy.

• The particles of a medium do not travel with the wave.

• Mechanical waves require a medium, but electromagnetic waves do not.

• Particles in a transverse wave vibrate perpen-dicularly to the direction the wave travels.

• Particles in a longitudi-nal wave vibrate parallel to the direction that the wave travels.

Using Key Terms

Complete each of the following sentences by choosing the correct term from the word bank.

transverse wave wavelongitudinal wave medium

1. In a , the particles vibrate parallel to the direction that the wave travels.

2. Mechanical waves require a through which to travel.

3. Any transmits energy through vibrations.

4. In a , the particles vibrate perpendicularly to the direction that the wave travels.

Understanding Key Ideas

5. Waves transfer

a. matter. c. particles.b. energy. d. water.

6. Name a kind of wave that does not require a medium.

Critical Thinking

7. Applying Concepts Sometimes,people at a sports event do “the wave.” Is this a real example of a wave? Why or why not?

8. Making Inferences Why can supernova explosions in space be seen but not heard on Earth?

Interpreting Graphics

9. Look at the figure below. Which part of the wave is the crest? Which part of the wave is the trough?

Topic: The Nature of Waves; Types of Waves

SciLinks code: HSM1017; HSM1574

b

a


Answers to Section Review

1. longitudinal wave2. medium3. wave4. transverse wave5. b6. electromagnetic wave7. No; the people just stand up on

their own and then sit down again. No energy is transmitted from one person to the next.

8. Light, an electromagnetic wave, does not require a medium through which to travel, so it is transmitted through space. Sound, however, requires a medium, so it cannot be transmitted through space.

9. a: crest; b: trough

CHAPTER RESOURCES


• Section Quiz g• Section Review g• Vocabulary and Section Summary g• SciLinks Activity g

CRF

READING STRATEGY

2 Properties of WavesYou are in a swimming pool, floating on your air mattress, enjoying a gentle breeze. Your friend does a “cannonball” from the high dive nearby. Suddenly, your mattress is rocking wildly on the waves generated by the huge splash.

The breeze generates waves in the water as well, but they arevery different from the waves created by your diving friend.The waves made by the breeze are shallow and close together,while the waves from your friend’s splash are tall and widelyspaced. Properties of waves, such as the height of the wavesand the distance between crests, are useful for comparing anddescribing waves.

AmplitudeIf you tie one end of a rope to the back of a chair, you cancreate waves by moving the free end up and down. If youshake the rope a little, you will make a shallow wave. If youshake the rope hard, you will make a tall wave.

The amplitudeamplitude of a wave is related to its height. A wave’samplitude is the maximum distance that the particles of amedium vibrate from their rest position. The rest position isthe point where the particles of a medium stay when thereare no disturbances. The larger the amplitude is, the taller thewave is. Figure 1 shows how the amplitude of a transversewave may be measured.

Larger Amplitude—More EnergyWhen using a rope to make waves, you have to work harder tocreate a wave with a large amplitude than to create one witha small amplitude. The reason is that it takes more energy tomove the rope farther from its rest position. Therefore, a wavewith a large amplitude carries more energy than a wave witha small amplitude does.

amplitudeamplitude the maximum distance that the particles of a wave’s medium vibrate from their rest position

Figure 1 The amplitude of a transverse wave is meas ured from the rest position to the crest or to the trough of the wave.

Rest position

Amplitude

What You Will Learn

Identify and describe fourwave properties.Explain how frequency andwavelength are related to thespeed of a wave.

Vocabularyamplitude frequencywavelength wave speed

Mnemonics As you read this section,create a mnemonic device to help youremember the wave equation.

OverviewThis section introduces propertiescommon to all types of waves.Students explore frequency,wavelength, amplitude, energycontent, and speed of waves.

BellringerBefore class, draw a longitudinalwave and a transverse wave onthe board or the overhead pro-jector. Have students draw thewaves and label the parts ofeach one.

Demonstration --------------gPitch of a Rubber Band Plucka rubber band so that it makes atone. Then, change the lengthof the rubber band so that thetone changes pitch. Ask studentsto explain what caused the pitchchange. Have them observe thewave (the vibration) in the rub-ber band as you repeat the dem-onstration. Lead students tothe conclusion that the tonechanges as the frequency ofthe wave changes. Explain thatthe frequency is the numberof waves produced in a givenamount of time. (You canalso use a guitar for thisdemonstration.) l Auditory

2

MISCONCEPTIONALERT

Amplitude of a Longitudinal Wave Theamplitude of a longitudinal wave is usu-ally measured as a difference in pressure(air pressure or otherwise) between thecompressions and rarefactions. Longitu-dinal waves are not discussed in terms ofpressure in the text, so this method ofmeasuring amplitude is not discussed.

CHAPTER RESOURCES


CRF • Lesson Plan• Directed Reading Ab, Bs

Technology

Transparencies • Bellringer

• P83 Measuring Wavelengths;Measuring Frequency

Workbooks


Math Skills for Science• Dividing Whole Numbers with

Long Divisiong


WavelengthAnother property of waves is wavelength. A wavelength isthe distance between any two crests or compressions next toeach other in a wave. The distance between two troughs orrarefactions next to each other is also a wavelength. In fact,the wavelength can be measured from any point on a waveto the next corresponding point on the wave. Wavelength ismeasured the same way in both a longitudinal wave and atransverse wave, as shown in Figure 2.

Shorter Wavelength—More EnergyIf you are making waves on either a spring or a rope, the rateat which you shake it will determine whether the wavelengthis short or long. If you shake it rapidly back and forth, thewavelength will be shorter. If you are shaking it rapidly, youare putting more energy into it than if you were shaking itmore slowly. So, a wave with a shorter wavelength carries moreenergy than a wave with a longer wavelength does.

✓Reading Check How does shaking a rope at different ratesaffect the wavelength of the wave that moves through the rope?(See the Appendix for answers to Reading Checks.)

wavelength the distance from anypoint on a wave to an identical pointon the next wave

Wavelength can be measured from any two corre-sponding points that are adjacent on a wave.

Measuring WavelengthsFigure 2

Springy Waves1. Hold a coiled spring toy

on the floor between youand a classmate so thatthe spring is straight. Thisis the rest position.

2. Move one end of thespring back and forth ata constant rate. Note thewavelength of the waveyou create.

3. Increase the amplitude ofthe waves. What did youhave to do? How did thechange in amplitude affectthe wavelength?

4. Now, shake the springback and forth about twiceas fast as you did before.What happens to thewavelength? Record yourobservations.

Wavelength

Wavelength

Longitudinal wave

Transverse wave

Wavelength

Wavelength

M A T E R I A LFOR EACH GROUP

• coiled spring toy or piece of rope

Answers

3. To increase the amplitude of the wave, thespring must be shaken farther with biggermotions. That is, the student must providemore energy to the wave. There should be

no effect on wavelength when amplitudeincreases. (It may be difficult to increaseamplitude without increasing frequency. Ifstudents increase frequency significantly,wavelength will change.)

4. The wavelength should become shorter asthe frequency is increased.


Shaking the rope faster makes thewavelength shorter; shaking therope more slowly makes the wave-length longer.

vv------------------------------------------b

Constructing a Transverse WaveProvide students with yarn andtape to construct a transversewave similar to the ones onthese pages. Ask them toincrease the amplitude of thewave while keeping the fre-quency constant. Have themexplain what increasing theamplitude represents. Then,have them change the fre-quency, and ask them what hap-pened to the wavelength. (Thewavelength decreased with anincrease in frequency, and itincreased with a decrease infrequency.)l Kinesthetic ee

StrategiesStrategiesINCLUSIONINCLUSION

• Gifted and Talented• Behavior Control IssuesSome students have a naturalcuriosity that drives them towant to know informationbeyond the textbook. Asksome of these students toresearch examples of jobswhere a person would needto figure out amplitude,wavelength, frequency, orwave speed. l Intrapersonal

SUPPORT FOR

English LanguageLearnersWave Heights Students maybe more open to learning ifthey realize they know some-thing on the topic already.Before reading, ask, “Based onwhat you know about waterwaves and tsunamis, what doesthe height of the wave mean?”Ask students to explain theirreasoning.l Logical

Section 2 • Properties of Waves 581

FrequencyThink about making rope waves again. The number of waves that you can make in 1 s depends on how quickly you move the rope. If you move the rope slowly, you make only a small number of waves each second. If you move it quickly, you make a large number of waves. The number of waves produced in a given amount of time is the frequencyof the wave. Frequency is usually expressed in hertz (Hz). For waves, one hertz equals one wave per second (1 Hz � 1/s). Figure 3 shows a wave with a frequency of 0.2 Hz.

✓Reading Check If you make three rope waves per second, what is the frequency of the wave?

Higher Frequency—More EnergyTo make high-frequency waves in a rope, you must shake the rope quickly back and forth. To shake a rope quickly takes more energy than to shake it slowly. Therefore, if the amplitudes are equal, high-frequency waves carry more energy than low-frequency waves.

Wave SpeedWave speed is the speed at which a wave travels. Wave speed (v) can be calculated using wavelength (l, the Greek letter lambda) and frequency (f ),by using the wave equation, which is shown below:

v � l � f

Figure 3 Frequency can be measured by counting how many waves pass by in a certain amount of time. Here, two waves went by in 10 s, so the frequency is 2 /10 s � 0.2 Hz.

Wave Calculations Determine the wave speed of a wave that has a wavelength of 5 m and a frequency of 4 Hz.

Step 1: Write the equation for wave speed.

v � l � f

Step 2: Replace the l and f with the values given in the problem, and solve.

v � 5 m � 4 Hz � 20 m/sThe equation for wave speed can also be re-

arranged to determine wavelength or frequency, as shown at top right.

Now It’s Your Turn1. What is the frequency of a wave if the

wave has a speed of 12 cm/s and a wave-length of 3 cm?

2. A wave has a frequency of 5 Hz and a wave speed of 18 m/s. What is its wave-length?

l � (Rearranged by dividing by f.)

(Rearranged by dividing by l.)

v

vf

f �l



3 Hz

Reteaching -------------------------------------bMeasuring Wavelength and Amplitude Have students take turns coming to the board and alternating between drawing a wave and then labeling the wave-length and (if it is a transverse wave) amplitude of that wave. Have the students that draw the waves alternate between drawing a transverse and longitudinal wave. l Visual/Interpersonal

Quiz ---------------------------------------------------------------------g

1. If wave speed is constant, as frequency increases, the _____ decreases. (wavelength)

2. _____ is the number of vibra-tions per second. (Frequency)

3. The distance between two cor-responding points on consec-utive waves is one _____. (wavelength)

4. As frequency increases, the _____ of the wave also increases. (energy)

Alternative Assessment ---------------------------g

Concept Mapping Have stu-dents make a concept map explaining how amplitude, wavelength, and frequency are related to the energy of a wave. l Visual

Answers to Math Focus

1. f � v/� � 12 cm/s � 3 cm � 4/s � 4 Hz

2. � � v/f � 18 m/s � 5 Hz � 18 m/s � 5/s � 3.6 m

Is That a Fact!Humans normally hear sounds with frequencies from 20 Hz to 20,000 Hz.



SummarySummary

Review

Frequency and Wavelength RelationshipThree of the basic properties of a wave are related to one another in the wave equation—wave speed, frequency, and wavelength. If you know any two of these properties of a wave, you can use the wave equation to find the third.

One of the things the wave equation tells you is the relation-ship between frequency and wavelength. If a wave is traveling a certain speed and you double its frequency, its wavelength will be cut in half. Or if you were to cut its frequency in half, the wavelength would be double what it was before. So, you can say that frequency and wavelength are inversely related.Think of a sound wave, traveling underwater at 1,440 m/s, given off by the sonar of a submarine like the one shown in Figure 4. If the sound wave has a frequency of 360 Hz, it will have a wavelength of 4.0 m. If the sound wave has twice that frequency, the wavelength will be 2.0 m, half as big.

The wave speed of a wave in a certain medium is the same no matter what the wavelength is. So, the wavelength and frequency of a wave depend on the wave speed, not the other way around.

frequency the number of waves produced in a given amount of time

wave speed the speed at which a wave travels through a medium

Figure 4 Submarines use sonar, sound waves in water, to locate underwater objects.

• Amplitude is the maxi-mum distance the parti-cles of a medium vibrate from their rest position.

• Wavelength is the distance between two adjacent corresponding parts of a wave.

• Frequency is the number of waves that pass a given point in a given amount of time.

• Wave speed can be calculated by multiplying the wave’s wavelength by the frequency.

Using Key Terms

1. In your own words, write a definition for each of the following terms: amplitude,frequency, and wavelength.


2. Which of the following results in more energy in a wave?

a. a smaller wavelengthb. a lower frequencyc. a shallower amplituded. a lower speed

3. Draw a transverse wave, and label how the amplitude and wavelength are measured.

Math Skills

4. What is the speed (v) of a wave that has a wavelength (l) of 2 m and a frequency (f ) of 6 Hz?

Critical Thinking

5. Making Inferences A wave has a low speed but a high frequency. What can you infer about its wavelength?

6. Analyzing Processes Two friends blow two whistles at the same time. The first whistle makes a sound whose frequency is twice that of the sound made by the other whistle. Which sound will reach you first?

Topic: Properties of WavesSciLinks code: HSM1236

Section 2 • Properties of Waves 583


1. Sample answer: amplitude: the maximum distance that the parti-cles of a wave vibrate from their rest positions; frequency: the number of vibrations per second of a wave; wavelength: the dis-tance between two correspond-ing points on a wave

2. a3. Answers should include a dia-

gram of a wave like the one in Figure 1, with amplitude indi-cated as shown in Figure 1, and wavelength indicated as shown in Figure 2.

4. v � � � f � 2 m � 6 Hz �12 m/s

5. Its wavelength must be short.6. Both sounds will reach you at

the same time: wave speed is not dependent on frequency, although the reverse is true.

CHAPTER RESOURCES


• Section Quiz g• Section Review g• Vocabulary and Section Summary g• Reinforcement Worksheet b• Datasheet for Quick Lab

CRF

READING STRATEGY

3 Wave InteractionsIf you’ve ever seen a planet in the night sky, you may have hada hard time telling it apart from a star. Both planets and starsshine brightly, but the light waves that you see are from verydifferent sources.

All stars, including the sun, produce light. But planets donot produce light. So, why do planets shine so brightly? Theplanets and the moon shine because light from the sun reflectsoff them. Without reflection, you would not be able to seethe planets. Reflection is one of the wave interactions thatyou will learn about in this section.

ReflectionReflectionReflection happens when a wave bounces back afterhitting a barrier. All waves—including water, sound, and lightwaves—can be reflected. The reflection of water waves is shownin Figure 1. Light waves reflecting off an object allow you tosee that object. For example, light waves from the sun arereflected when they strike the surface of the moon. Thesereflected waves allow us to enjoy moonlit nights. A reflectedsound wave is called an echo.

Waves are not always reflected when they hit a barrier. Ifall light waves were reflected when they hit your eyeglasses,you would not be able to see anything! A wave is transmittedthrough a substance when it passes through the substance.

Figure 1 These water waves are reflecting off the side of the container.

reflectionreflection the bouncing back of aray of light, sound, or heat when theray hits a surface that it does not gothrough

What You Will Learn

Describe reflection, refraction,diffraction, and interference.Compare destructive interferencewith constructive interference.Describe resonance, andgive examples.

Vocabularyreflection interferencerefraction standing wavediffraction resonance

Reading Organizer As you readthis section, make a concept mapby using the terms above.

OverviewIn this section, students explorehow waves reflect, refract, or dif-fract when interacting with adifferent medium or barrier.Students also learn how wavesinterfere with other waves.

BellringerWrite v, f, and � on the board.Have students write each sym-bol, what each symbol standsfor, and how each symbol relatesto the other two.

vv---------------------------------------------------g

Wave Interactions Use two dif-ferent types of springs. A long,tightly coiled spring, oftencalled a snake, and a large,coiled spring toy are ideal. Usinga strong cord, tie one end ofeach spring together, forming a“spring rope.” Have two volun-teers sit about 3 m apart on thefloor. Have one student hold thespring rope on the floor whilethe other creates transversewaves by moving the springfrom side to side. Ask the classto observe what happens at theboundary between the twosprings when a wave passes fromone spring to the other. (Studentsshould see a change in the wave’sspeed and wavelength.) l Visual

3

Is That a Fact!The reflection of sound is called anecho. If you are closer than 15 m to areflecting wall, you cannot hear anecho. The brain requires a 0.1 s delay toperceive an echo, and at less than 15 m,the sound wave would be reflected backfrom the wall in less than 0.1 s.

CHAPTER RESOURCES


CRF • Lesson Plan• Directed Reading Ab• Directed Reading Bs

Technology

Transparencies• Bellringer

Workbooks



RefractionTry this simple activity: Place a pencil in a half-filled glass ofwater. Now, look at the pencil from the side. The pencil appearsto be broken into two pieces! But as you can see when youtake the pencil out of the water, it is still in one piece.

What you saw in this experiment was the result of therefraction of light waves. Refraction is the bending of a waveas the wave passes from one medium to another at an angle.Refraction of a flashlight beam as the beam passes from air towater is shown in Figure 2.

When a wave moves from one medium to another, thewave’s speed changes. When a wave enters a new medium,the wave changes wavelength as well as speed. As a result, thewave bends and travels in a new direction.

✓Reading Check What happens to a wave when it movesfrom one medium to another at an angle? (See the Appendix foranswers to Reading Checks.)

Refraction of Different ColorsWhen light waves from the sun pass through a droplet of waterin a cloud or through a prism, the light is refracted. But thedifferent colors in sunlight are refracted by different amounts,so the light is dispersed, or spread out, into its separate colors.When sunlight is refracted this way through water droplets,you can see a rainbow. Why does that happen?

Although all light waves travel at the same speed throughempty space, when light passes through a medium such aswater or glass, the speed of the light wave depends on thewavelength of the light wave. Because the different colors oflight have different wavelengths, their speeds are different, andthey are refracted by different amounts. As a result, the colorsare spread out, so you can see them individually.

refraction the bending of a waveas the wave passes between twosubstances in which the speed of thewave differs

Figure 2 A light wave passingat an angle into a new medium—such as water—is refractedbecause the speed of the wavechanges.

WRITINGSKILL

The Colors of theRainbow People

have always been fascinatedby the beautiful array ofcolors that results when sun-light strikes water droplets inthe air to form a rainbow. Theknowledge science gives usabout how they form makesthem no less breathtaking.

In the library, find a poemthat you like about rainbows.In your science journal,copy the poem, and writea paragraph in which youdiscuss how your knowledgeof refraction affects youropinion about the poem.

Demonstration --------------gRefraction Display a largebeaker half-filled with water.Place a ruler in the water, andrest it against the side. Have stu-dents observe the ruler from allsides. Have students record theirobservations and describe howthe ruler appears to change whenobserved from different angles.Ask them to predict how theruler would look if light enteredthe water perpendicularly to thesurface. (The light would not refract,and the ruler would not look bent.)l Logical


It refracts.

Using the Figure -----g

Light Refraction Use Figure 2to show students how a wavebends during refraction. Pointout that a wave that enters anew medium at a 90˚ angle fromthe surface of the medium willnot refract because the entirewave enters the new mediumat the same time. Therefore, theentire wave changes speed atthe same time and does notbend. It may be helpful to drawa diagram similar to Figure 2that shows a wave passing fromone medium to another at a 90°angle. l Visual

MISCONCEPTIONALERT

Refraction and Frequency Studentsmay think that as a wave enters a differ-ent medium and changes speed, its fre-quency also changes. Be sure studentsunderstand that when a wave changesspeed, its wavelength changes but itsfrequency remains the same. Frequencyis dependent on the source, not on themedium.

Section 3 • Wave Interactions 585

DiffractionSuppose you are walking down a city street and you hear music.The sound seems to be coming from around the corner, butyou cannot see where the music is coming from because abuilding on the corner blocks your view. Why do sound wavestravel around a corner better than light waves do?

Most of the time, waves travel in straight lines. For example,a beam of light from a flashlight is fairly straight. But in somecircumstances, waves curve or bend when they reach the edgeof an object. The bending of waves around a barrier or throughan opening is known as diffraction.

If You Can Hear It, Why Can’t You See It?The amount of diffraction of a wave depends on its wavelengthand the size of the barrier or opening the wave encounters, asshown in Figure 3. You can hear music around the corner of abuilding because sound waves have long wavelengths and areable to diffract around corners. However, you cannot see whois playing the music because the wavelengths of light wavesare much shorter than sound waves, so light is not diffractedvery much.

diffraction a change in thedirection of a wave when thewave finds an obstacle or anedge, such as an opening

Figure 3 Diffraction Through an Opening

If the barrier oropening is largerthan the wave-length of the wave,there is only asmall amount ofdiffraction.

If the barrier oropening is thesame size orsmaller than thewavelength of anapproaching wave,the amount ofdiffraction is large.

What if Light Diffracted?With an adult, take a walkaround your neighborhood.Light waves diffract aroundcorners of buildings muchless than sound waves do.Imagine what would hap-pen if light waves diffractedaround corners much morethan sound waves did. Writea paragraph in your sciencejournal describing how thiswould change what you seeand hear as you walk aroundyour neighborhood.

CONNECTIONCONNECTION vvReal World --------------------------------------------g

Interfering Headphones Insome occupations, workers areexposed to noise with ampli-tudes or frequencies that can beharmful. Now there are head-phones available that createdestructive interference to can-cel the dangerous noise. Theseheadphones receive the noisethat the wearer hears, processthe sounds, and then producedestructive interference to reduceor cancel the outside noise.

Have students think of and dis-cuss situations in which theseheadphones would be useful.l Intrapersonal

vv--------------------------------------a

AM and FM Radio Waves Havestudents research AM and FMradio waves. Ask students thefollowing questions: What arethe differences between them?Why is it harder to receive FMbroadcasts in some places? Whycan AM broadcasts be heard forgreat distances under certainconditions? l Logical

Answer to School-to-HomeActivity

Sample answer: I could see aroundcorners, so I could avoid runninginto people. I could see oncomingtraffic. I could look under or aroundfurniture or other objects to findmissing items. But I wouldn’t beable to hear people calling me fromanother room. I wouldn’t be able tohear oncoming traffic.

SUPPORT FOR

English Language LearnersRefraction and Refl ection Studentsmay need help distinguishing betweenrefraction and refl ection. Have themread the paragraphs aloud to a partner.Model pronunciation as needed. To besure the listeners can discern the words,have them show white cards for refrac-tion and red for reflection. If a wrongcard is shown, the reader should ask theteacher to listen to determine if the er-ror is productive or receptive and correctaccordingly.l Verbal/Auditory


Transparencies• P84 Constructive and Destructive Interference


Waves approaching

Waves continuing

Waves overlapping Waves continuing

Waves approaching Waves overlapping

InterferenceYou know that all matter has volume. Therefore, objects cannot be in the same space at the same time. But waves are energy, not matter. So, more than one wave can be in the same place at the same time. In fact, two waves can meet, share the same space, and pass through each other! When two or more waves share the same space, they overlap. The result of two or more waves overlapping is called interference. Figure 4shows what happens when waves occupy the same space and interfere with each other.

Constructive InterferenceConstructive interference happens when the crests of one wave overlap the crests of another wave or waves. The troughs of the waves also overlap. When waves combine in this way, the energy carried by the waves is also able to combine. The result is a new wave that has higher crests and deeper troughs than the original waves had. In other words, the resulting wave has a larger amplitude than the original waves had.

✓Reading Check How does constructive interference happen?

Figure 4 Constructive and Destructive Interference

Constructive Interference When waves combine by constructive interference, the combined wave has a larger amplitude.

Destructive Interference When two waves with the same amplitude combine by destructive interference, they cancel each other out.

interference the combination of two or more waves that results in a single wave


vv--------------------------------------------------------b

Creating Interference Providepairs of students with a large, coiled spring. Instruct them to stretch it out between them while sitting on the floor. Instruct students to create con-structive and destructive interfer-ence in the spring by sitting holding opposite ends of the barely stretched spring on a slick floor. Have one student make transverse waves by waggling the spring to one side sharply and watch the waves move along the spring. Have the student at the other end make a wave the same way. If two students simultane-ously make a wave, one to his or her left and the other to his or her right, the waves should inter-fere constructively. If they make waves each to their right (or left), they will see destructive interfer-ence. Ask them what happens to the spring when the waves meet in constructive interference. (Onewave forms, and its amplitude is greater than the amplitudes of the individual waves. The amplitude is the sum of the amplitudes of the original waves.) Then ask them what happens during destructive interference. (The amplitude of the new wave is the difference between the amplitudes of the original waves.) l Kinesthetic


Constructive interference occurs when the crests of one wave over-lap the crests of another wave.

Microwave Interference Food heated in a microwave oven sometimes has hot spots and cold spots. This problem may be caused by interference. Constructiveinterference, which increases the ampli-tude of the microwaves, can cause hot spots. Destructive interference, which decreases the amplitude of the waves, can cause cold spots.

MISCONCEPTIONALERT

Interference of Waves Interference occurs only in the region where the waves overlap. After the waves pass through this region, they continue on as if they had never met.

Figure 5 When you move a ropeat certain frequencies, you cancreate different standing waves.

Figure 6 A marimba produces notesthrough the resonance of air columns.

Destructive interference

Constructive interference

Destructive InterferenceDestructive interference happens when the crests of one waveand the troughs of another wave overlap. The new wave hasa smaller amplitude than the original waves had. When thewaves involved in destructive interference have the same ampli-tude and meet each other at just the right time, the result isno wave at all.

Standing WavesIf you tie one end of a rope to the back of a chair and move theother end up and down, the waves you make go down the ropeand are reflected back. If you move the rope at certain frequen-cies, the rope appears to vibrate in loops, as shown in Figure 5.The loops come from the interference between the wave youmade and the reflected wave. The resulting wave is called astanding wave. In a standing wave, certain parts of the waveare always at the rest position because of total destructiveinterference between all the waves. Other parts have a largeamplitude because of constructive interference.

A standing wave only looks as if it is standing still. Wavesare actually going in both directions. Standing waves can beformed with transverse waves, such as when a musician plucksa guitar string, as well as with longitudinal waves.

✓Reading Check How can interference and reflection causestanding waves?

The vibrating barscause the air in thecolumns to vibrate.

The lengths of the columns havebeen adjusted so that the reso-nant frequency of the air columnmatches the frequency of the bar.

c

The air column resonates with thebar, increasing the amplitude of thevibrations to produce a loud note.

d

b

The marimba bars arestruck with a mallet,causing the bars tovibrate.

a


A standing wave results from a wave that isreflected between two fixed points. Interferencefrom the wave and reflected waves causes cer-tain points to remain at rest and certain pointsto remain at a large amplitude.

Reteaching -------------------------------------bWave Interactions Table Onthe board, make a table withthree columns and five rows.Fill in the first row with “Waveinteraction,” “Cause,” and“Effect.” Fill in the first columnwith “Reflection,” “Refraction,”“Diffraction,” and “Interference.”Call on different students to fillin the different spaces in thetable, indicating what causeseach wave interaction and whateffect each has on a wave.l Visual

Quiz ---------------------------------------------------------------------g

1. When a wave bounces backfrom a barrier, _____ hasoccurred. (reflection)

2. _____ occurs when a wavebends as it passes at an anglefrom one medium to a differ-ent medium. (Refraction)

3. _____ happens when two ormore waves overlap.(Interference)

AlternativeAssessment ---------------------------g

Concept Mapping Have stu-dents create a concept mapusing as many vocabulary wordsfrom this chapter as they can.Then, provide groups of stu-dents with yarn, poster board,glue, tape, and scissors. Eachgroup should construct a modelfor the concepts on its map.l Visual

h-----------------------------g

Research Resonance is a very importantconcept in music. Have students conductresearch to learn how resonance affects thesounds produced by different musicalinstruments. Students can share theirresults by writing a report, by making aposter, or by playing a musicalinstrument. l Logical



SummarySummary

Review

ResonanceThe frequencies at which standing waves are made are calledresonant frequencies. When an object vibrating at or near theresonant frequency of a second object causes the second objectto vibrate, resonanceresonance occurs. A resonating object absorbs energyfrom the vibrating object and vibrates, too. An example ofresonance is shown in Figure 6 on the previous page.

You may be familiar with another example of resonanceat home—in your shower. When you sing in the shower, cer-tain frequencies create standing waves in the air that fills theshower stall. The air resonates in much the same way that theair column in a marimba does. The amplitude of the soundwaves becomes greater. So your voice sounds much louder.

standing wavestanding wave a pattern of vibration that simulates a wave that is standing still

resonanceresonance a phenomenon that occurs when two objects naturally vibrate at the same frequency; the sound produced by one object causes the other object to vibrate

•• Waves reflect after hitting a barrier.

•• Refraction is the bending of a wave when it passes through different media.

•• Waves bend around bar-riers or through open-ings during diffraction.

•• The result of two or more waves overlapping is called interference.

•• Amplitude increases during constructive inter-ference and decreases during destructive interference.

•• Resonance occurs when a vibrating object causes another object to vibrate at one of its resonant frequencies.

Using Key Terms

Complete each of the followingsentences by choosing the correctterm from the word bank.

refraction reflectiondiffraction interference

1. happens when a wave passesfrom one medium to another atan angle.

2. The bending of a wave around abarrier is called .

3. We can see the moon because ofthe of sunlight off it.


4. The combining of waves as theyoverlap is known as

a. interference.b. diffraction.c. refraction.d. resonance.

5. Name two wave interactionsthat can occur when a waveencounters a barrier.

6. Explain why you can hear twopeople talking even after theywalk around a corner.

7. Explain what happens when twowaves encounter one another indestructive interference.

Critical Thinking

8. Making Inferences Sometimes,when music is played loudly,you can feel your body shake.Explain what is happening interms of resonance.

9. Applying Concepts Howcould two waves on a ropeinterfere so that the rope didnot move at all?

Interpreting Graphics

10. In the image below, what sort ofwave interaction is happening?

Topic: Interactions of WavesSciLinks code: HSM0805


1. refraction2. diffraction3. reflection4. a5. reflection and diffraction6. You can hear people talk-

ing even if you cannot seethem because sound wavesdiffract.

7. When the crest of onewave coincides with the troughof another wave and they over-lap, the result is a cancellationof both waves.

8. The frequency of the soundwaves is near one of yourbody’s resonant frequencies.This causes your body tovibrate. In other words, yourbody is in resonance with themusic.

9. If a crest of one wave hit atrough of another wave on arope, the two waves wouldcancel each other out.

10. constructive interference

CHAPTER RESOURCES


• Section Quizg• Section Reviewg• Vocabulary and Section Summaryg• Reinforcement Worksheetb• Critical Thinkinga

CulturalAwarenessCulturalAwareness g

Marimbas The marimba is an instru-ment of African origin that is similar toa xylophone.

CRF


Using Scientifi c Methods

LabSkills Practice

Form hypotheses about theenergy and speed of waves.

Test your hypotheses byperforming an experiment.

• beaker, small

• newspaper

• pan, shallow, approximately20 cm × 30 cm

• pencils (2)

• stopwatch

• water

Wave Energy and SpeedIf you threw a rock into a pond, waves would carry energyaway from the point of origin. But if you threw a large rockinto a pond, would the waves carry more energy away from thepoint of origin than waves caused by a small rock? And woulda large rock make waves that move faster than waves madeby a small rock? In this lab, you’ll answer these questions.

Ask a Question

1 In this lab, you will answer the following questions: Dowaves made by a large disturbance carry more energy thanwaves made by a small disturbance? Do waves created by alarge disturbance travel faster than waves created by a smalldisturbance?

Form a Hypothesis

2 Write a few sentences that answer the questions above.

Test the Hypothesis

3 Place the pan on a few sheets of newspaper. Using the smallbeaker, fill the pan with water.

4 Make sure that the water is still. Tap the surface of the waterwith the eraser end of one pencil. This tap represents thesmall disturbance. Record your observations about the size ofthe waves that are made and the path they take.

OBJECTIVES

MATERIALS

SAFETY

Skills PracticeSkills Practice LabLab

Wave Energy andSpeed

Teacher’s Notes

Time RequiredOne 45-minute class period

Lab Ratings

rTeacher Prep f

Student Set-Up ff

Concept Level ff

Clean Up ff

M A T E R I A L SThe materials listed are for eachgroup of 2–4 students.

Safety CautionRemind students to review allsafety cautions and icons beforebeginning this lab activity.

Procedure NotesFinding enough stopwatches forall students may be difficult. Stu-dents may have watches that canserve as timers or stopwatches.

Form a Hypothesis

2. Sample answer: Waves madeby a large disturbance carrymore energy than waves madeby a small disturbance andtravel faster than waves cre-ated by a small disturbance.

CHAPTER RESOURCES


CRF • Datasheet for Chapter Lab• Lab Notes and Answers

Technology

Classroom Videos• Lab Video

• Wave Speed, Frequency, and WavelengthJennifer Ford

North Ridge Middle SchoolNorth Richland Hills, Texas

Holt Lab Generator CD-ROMSearch for any lab by topic, standard, difficulty level,or time. Edit any lab to fit your needs, or create yourown labs. Use the Lab Materials QuickList softwareto customize your lab materials list.

CLASSROOM

TESTED& APPRO

VED


5 Repeat step 4. This time, use the stopwatch torecord the amount of time it takes for one ofthe waves to reach the side of the pan. Recordyour data.

6 Using two pencils at once, repeat steps 4 and5. These taps represent the large disturbance.(Try to use the same amount of force to tapthe water that you used with just one pencil.)Observe and record your results.

Analyze the Results

1 Describing Events Compare the appearanceof the waves created by one pencil with that ofthe waves created by two pencils. Were thereany differences in amplitude (wave height)?

2 Describing Events Compare the amount oftime required for the waves to reach the sideof the pan. Did the waves travel faster whentwo pencils were used?

Draw Conclusions

3 Drawing Conclusions Do waves made bya large disturbance carry more energy thanwaves made by a small one? Explain youranswer, using your results to support youranswer. (Hint: Remember the relationshipbetween amplitude and energy.)

4 Drawing Conclusions Do waves made bya large disturbance travel faster than wavesmade by a small one? Explain your answer.

Applying Your DataA tsunami is a giant ocean wave that can reacha height of 30 m. Tsunamis that reach land cancause injury and enormous property damage.Using what you learned in this lab about waveenergy and speed, explain why tsunamis areso dangerous. How do you think scientists canpredict when tsunamis will reach land?

Analyze the Results

1. The waves created by twopencils had a larger amplitudethan the waves created by onepencil.

2. The amount of time it took forthe waves to reach the side ofthe pan was the same for bothtrials. The waves appeared totravel at the same rate.

Draw Conclusions

3. yes; The large disturbance cre-ates waves with a large ampli-tude. Because amplitude isrelated to energy, waves cre-ated by a large disturbancecarry more energy.

4. no; All the waves appear totravel at the same speedbecause the times recorded forboth trials were the same.

Applying Your DataTsunamis have large amplitudes, sothey carry a lot of energy that cancause injury and property damage. Allwaves in the ocean travel at the samespeed. Therefore, scientists candetermine when a tsunami willreach land.

Lab NotesYou may wish to do this lab as ateacher demonstration using aglass pan and an overheadprojector.

CHAPTER RESOURCESWorkbooks

Whiz-Bang Demonstrations• Pitch Forksg

Long-Term Projects & Research Ideas• It’s a Whale of a Wavea

Chapter 20 • Chapter Lab 591

For each pair of terms, explain how the meanings of the terms differ.

1 longitudinal wave and transverse wave

2 wavelength and amplitude

3 refl ection and refraction

Multiple Choice

4 As the wavelength increases, the frequency

a. decreases.b. increases.c. remains the same.d. increases and then decreases.

5 Waves transfer

a. matter. c. particles.b. energy. d. water.

6 Refraction occurs when a wave enters a new medium at an angle because

a. the frequency changes.b. the amplitude changes.c. the wave speed changes.d. None of the above

7 The wave property that is related to the height of a wave is the

a. wavelength.b. amplitude.c. frequency.d. wave speed.

8 During constructive interference,

a. the amplitude increases.b. the frequency decreases.c. the wave speed increases.d. All of the above

9 Waves that don’t require a medium are

a. longitudinal waves.b. electromagnetic waves.c. surface waves.d. mechanical waves.

Short Answer

0 Draw a transverse wave and a longitudinal wave. Label a crest, a trough, a compression, a rarefac-tion, and wavelengths. Also, label the amplitude on the transverse wave.

q What is the relationship between frequency, wave speed, and wavelength?

Math Skills

w A fi sherman in a row boat notices that one wave crest passes his fi shing line every 5 s. He estimates the distance between the crests to be 1.5 m and estimates that the crests of the waves are 0.5 m above the troughs. Using this data, determine the amplitude and speed of the waves.

USING KEY TERMS

UNDERSTANDING KEY IDEAS

10. Answers should include a transverse and longitudinal wave with a correctly labeled crest, trough, and amplitude in the trans-verse wave and compression and rarefac-tion in the longitudinal wave, as shown earlier in this chapter.

11. Wave speed is the frequency multiplied by the wavelength. The longer the wavelength, the lower the frequency. The shorter the wavelength, the higher the frequency.

12. f � 1/5 s � 0.2 Hz; � � 1.5 m; v � � � f �

1.5 m � 0.2 Hz � 0.3 m/s. Amplitude � 0.5 m � 2 � 0.25 m

ANSWERS

Using Key Terms1. A longitudinal wave is a

wave that moves parallel to the direction of the disturbance of the particles. A transverse wave is a wave that moves per-pendicular to the direction of the disturbance of the particles.

2. Wavelength is the distance between corresponding points on a wave. Amplitude is the maximum distance that the medium is displaced by the wave.

3. Reflection occurs when a wave strikes a barrier and reverses direction. Refraction occurs when a wave enters a different medium and its speed and direction change.

Understanding Key Ideas4. a5. b6. c7. b8. a9. b

Assignment GuideSECTION QUESTIONS

1 1, 5, 9, 14

2 2, 4, 7, 10–12, 17

3 3, 6, 8, 13, 15–16


e Concept Mapping Use the followingterms to create a concept map:wave, refraction, transverse wave,longitudinal wave, wavelength,wave speed, and diffraction.

rAnalyzing Ideas You have lost thepaddles for the canoe you rented, andthe canoe has drifted to the center ofa pond. You need to get it back to theshore, but you do not want to get wetby swimming in the pond. Your friendsuggests that you drop rocks behindthe canoe to create waves that willpush the canoe toward the shore. Willthis solution work? Why or why not?

tApplying Concepts Some opera singerscan use their powerful voices to breakcrystal glasses. To do this, they singone note very loudly and hold it fora long time. While the opera singerholds the note, the walls of the glassmove back and forth until the glassshatters. Explain in terms of resonancehow the glass shatters.

yAnalyzing Processes After setting upstereo speakers in your school’s musicroom, you notice that in certain areasof the room, the sound from thespeakers is very loud. In other areas,the sound is very soft. Using the con-cept of interference, explain why thesound levels in the music room vary.

uPredicting Consequences A certainsound wave travels through water witha certain wavelength, frequency, andwave speed. A second sound wave withtwice the frequency of the fi rst wavethen travels through the same water.What is the second wave’s wavelengthand wave speed compared to those ofthe fi rst wave?

i Look at the waves below. Rank thewaves from highest energy to lowestenergy, and explain your reasoning.

a.

b.

c.

INTERPRETING GRAPHICS

CRITICAL THINKING

Critical Thinking13. An answer to this

exercise can befound at the endof this book.

14. Waves carry energy, not matter.So, waves will make the canoebob up and down in the pondbut will not push the canoecloser to the shore.

15. The vibrations from the singer’svoice cause the glass to vibrateat one of its resonant frequen-cies. It does not take much tomake it vibrate with a largeamplitude. But the glass is notvery flexible, so it shatters.

16. With constructive interference,the crest of one wave overlapswith the crest of another wave,making a new wave with ahigher crest and greater ampli-tude or loudness. With destruc-tive interference, the crest ofone wave overlaps with thetrough of another wave,decreasing the amplitude andmaking the sound softer.

17. The second wave will havehalf the wavelength of the firstwave and the same wavespeed. (Wave Speed dependson the medium, and not onwavelength or frequency.)

Interpreting Graphics18. rank: b, c, a

Wave b has a high frequencyand a large amplitude. Wave chas a high frequency and asmall amplitude. Wave a hasa low frequency and a smallamplitude.high frequency and largeamplitude = more energylow frequency and smallamplitude = less energy

CHAPTER RESOURCES


CRF • Chapter Reviewg• Chapter Test Ag• Chapter Test Ba• Chapter Test Cs• Vocabulary Activityg

Workbooks

Study Guide• Study Guide is also available in Spanish.

Chapter 20 • Chapter Review 593

READING

MISCONCEPTIONALERT

Teacher’s NoteTeacher’s NoteTo provide practice under more realistic testing conditions, give students 20 minutes to answer all of the questions in this Standardized Test Preparation.

Answers to the standardized test preparation can help you identify student misconcep-tions and misunderstandings.

READINGRead each of the passages below. Then, answer the questions that follow each passage.

Passage 1 On March 27, 1964, a powerful earth-quake rocked Alaska. The earthquake started on land near Anchorage, and the seismic waves spread quickly in all directions. The earthquake created a series of ocean waves called tsunamisin the Gulf of Alaska. In the deep water of the gulf, the tsunamis were short and far apart. But as these waves entered the shallow water surround-ing Kodiak Island, off the coast of Alaska, they became taller and closer together. Some reached heights of nearly 30 m! The destructive forces of the earthquake and tsunamis killed 21 people and caused $10 million in damage to Kodiak, which made this marine disaster the worst in the town’s 200-year history.

1. In the passage, what does tsunami mean?

A a seismic waveB an earthquakeC an ocean waveD a body of water

2. Which of these events happened fi rst?

F The tsunamis became closer together.G Tsunamis entered the shallow water.H Tsunamis formed in the Gulf of Alaska.I An earthquake began near Anchorage.

3. Which conclusion is best supported by information given in the passage?

A Kodiak had never experienced a tsunami before 1964.

B Tsunamis and an earthquake were the cause of Kodiak’s worst marine disaster in 200 years.

C Tsunamis are common in Kodiak.D The citizens of Kodiak went into debt after

the 1964 earthquake.

Passage 2 Resonance was partially responsiblefor the destruction of the Tacoma Narrows Bridge, in Washington. The bridge opened in July 1940 and soon earned the nickname Galloping Gertie because of its wavelike motions. These motions were created by wind that blew across the bridge. The wind caused vibrations that were close to a reso nant frequency of the bridge. Because the bridge was in resonance, it absorbed a large amount of energy from the wind, which caused it to vibrate with a large amplitude. On November 7, 1940, a supporting cable slipped, and the bridge began to twist. The twisting of the bridge, combined with high winds, further increased the amplitude of the bridge’s motion. Within hours, the amplitude became so great that the bridge collapsed. Luckily, all of the people on the bridge that day were able to escape before it crashed into the river below.

1. What caused wavelike motions in the Tacoma Narrows Bridge?

A wind that caused vibrations that were close to the resonant frequency of the bridge

B vibrations from cars going over the bridgeC twisting of a broken support cableD an earthquake

2. Why did the bridge collapse?

F A supporting cable slipped.G It absorbed a great amount of energy from

the wind.H The amplitude of the bridge’s vibrations

became great enough.I Wind blew across it.


Passage 11. C2. I3. B

Question 3: The passage implies that the disaster described involved the largest tsunami in the history of Kodiak, but it does not say that a tsu-nami had never struck Kodiak before. It also does not imply that tsunamis are common in Kodiak. The passage states the monetary cost of the dam-age but does not state that it caused the town to go into debt. Answer B is the most reasonable choice.

Passage 21. A2. H Question 2: Some students may choose

answer F. Although the slippage of a supporting cable ultimately led to the bridge’s collapse, the more direct cause of its collapse was when the amplitude of the bridge’s vibrations became great enough.

Sta

nd

ardized

Test P

rep

ara

tion

cm 1 2 3

Use the figure below to answer the ques-tions that follow.

1. This wave was generated in a laboratory investigation. What is the wavelength of the wave?

A 1.5 cmB 1.7 cmC 2.0 cmD 2.7 cm

2. If the frequency of the wave shown were doubled, what would the wavelength of the wave be?

F 0.85 cmG 1.35 cmH 3.4 cmI 5.4 cm

3. What is the amplitude of the wave shown?

A 0.85 cmB 1.7 cmC 2.7 cmD There is not enough information to

determine the answer.

Read each question below, and choose the best answer.

1. How is the product of 5 × 5 × 5 × 2 × 2 × 2 × 2 expressed in exponential notation?

A 35 × 42

B 53 × 24

C 57 × 27

D 107

2. Mannie purchased 8.9 kg of dog food from the veterinarian. How many grams of dog food did he purchase?

F 8,900 gG 890 gH 89 gI 0.89 g

3. What is the area of a rectangle whose sides are 3 cm long and 7.5 cm long?

A 10.5 cm2

B 12 cm2

C 21 cm2

D 22.5 cm2

4. An underwater sound wave traveled 1.5 km in 1 s. How far would it travel in 4 s?

F 5.0 kmG 5.5 kmH 6.0 kmI 6.5 km

5. During a tennis game, the person serving the ball is allowed only 2 serves to start a point. Hannah plays a tennis match and is able to use 50 of her 63 fi rst serves to start a point. What is the best estimate of Hannah’s fi rst-service percentage?

A 126%B 88%C 81.5%D 79%

INTERPRETING GRAPHICS MATH INTERPRETING GRAPHICS1. B2. F3. D

Question 1: Students may be tempted to choose D if they simply read the marking on the ruler at 2.7 cm. The wave begins at the 1.0 cm marking, however, so its wavelength is 2.7 cm � 1.0 cm � 1.7 cm.

MATH1. B2. F3. D4. H5. D

Question 5: The first sentence of this question is extraneous informa-tion. The question only asks for per-centage of first serves, and how many attempts at a serve the player is allowed does not actually pertain to the question.

CHAPTER RESOURCES


CRF • Standardized Test Preparation g

State Resources

For specifi c resources for your state, visit go.hrw.com and type in the keyword HSMSTR.

Chapter 20 • Standardized Test Preparation 595

in Action

in Action

MathRadio waves travel about 300,000,000 m/s.The M100 galaxy is about 5.68 × 1023 maway from Earth. How long, in years, does ittake radio waves from M100 to be detectedby the VLA?

Language ArtsThomas Young said, “The natureof light is a subject of no mate-

rial importance to the concerns of life orto the practice of the arts, but it is in manyother respects extremely interesting.” Writea brief essay in which you answer the fol-lowing questions: What do you think Youngmeant? Do you agree with him? Howwould you respond to his statement?

WRITINGSKILL

Scientific DiscoveriesThe Wave Nature of LightHave you ever wondered what light reallyis? Many early scientists did. One of them,the great 17th-century scientist Isaac New-ton, did some experiments and decided thatlight consisted of particles. But when experi-menting with lenses, Newton observed somethings that he could not explain.

Around 1800, the scientist ThomasYoung did more experiments on light andfound that it diffracted when it passedthrough slits. Young concluded that lightcould be thought of as waves. Althoughscientists were slow to accept this idea, theynow know that light is both particle-like andwavelike.

Science, Technology,and SocietyThe Ultimate TelescopeThe largest telescopes in the world don’tdepend on visible light, lenses, or mirrors.Instead, they collect radio waves from the farreaches of outer space. One radio telescope,called the Very Large Array (VLA), is locatedin a remote desert in New Mexico.

Just as you can detect light waves fromstars with your eyes, radio waves emittedfrom objects in space can be detected withradio telescopes. The Very Large Array con-sists of 27 radio telescopes like the ones inthe photo above.

Science, Technology,

and Society

BackgroundA radio telescope collects radiowaves, just as an optical tele-scope collects visible light.However, to bring radio wavesinto sharp focus, a radio tele-scope must be much larger thanan optical telescope becauseradio waves have much longerwavelengths than visible lightwaves do.

Scientific Discoveries

BackgroundNewton could not explain thecurious phenomenon of colored“rings” that he noted when heplaced two lenses on top of eachother, because it did not fit inwith his corpuscular theory ofthe nature of light. When revis-ited by Young, this interferenceeffect of light was shown to beone of the best proofs of thewave nature of light.

Thomas Young’s demonstrationof the interference of light madelittle impression when Youngannounced it in 1803. It tookanother decade of studies andexperiments by Augustin Fresnel(1788–1827) to convince thestaunchest of Newton’s sup-porters of the wave nature oflight.

Answer to Math Activity

d � r � tt � d � rt � 5.68 � 1023 m � 300,000,000 m/s �

1.89 � 1015 sseconds/year � 60 s/min � 60 min/h �

24 h/day � 365 days/year � 3.15 � 107 s/year1.89 � 1015 s � 3.15 � 107 s/year � 6.00 � 107

(60 million) years

Answer to Language Arts Activity

Sample answer: Thomas meant that you don’tneed to know anything about light in order touse it and appreciate it. Nevertheless, thenature of light is very interesting. I think he wascorrect. Without needing to worry aboutwhether light consists of particles or waves,visual artists make good use of light effects andpeople can see light. But the question of whatlight is is still interesting.


Social StudiesResearch the different ways in which ultrasound technology is

used in medical practice today. Write a few paragraphs about what you learn.

To learn more about these Science in Action topics, visitgo.hrw.com and type in thekeyword HP5WAVF.

Check out Current Science®

articles related to this chapter by visiting go.hrw.com. Just type in the keyword HP5CS20.

WRITINGSKILL

Estela ZavalaUltrasonographer Estela Zavala is a registered diagnostic medical ultrasonographer who works at Austin Radiological Association in Austin, Texas. Most people have seen a picture of a sonogram showing an unborn baby inside its mother’s womb. Ultrasound technologists make these images with an ultrasound machine, which sends harmless, high-frequency sound waves into the body. Zavala uses ultrasound to form images of organs in the body. Zavala says about her education, “After graduating from high school, I went to an X-ray school to be licensed as an X-ray technologist. First, I went to an intensive one-month training program. After that, I worked for a licensed radiol-ogist for about a year. Finally, I attended a year-long ultrasound program at a local community college before becoming fully licensed.” What Zavala likes best about her job is being able to help people by finding out what is wrong with them without surgery. Before ultrasound, surgery was the only way to find out about the health of someone’s organs.

Chapter 20 • Science in Action 597

Careers

BackgroundWhen ultrasound waves pass from one material to different material, such as from muscle tissues to the lungs, some of the waves are reflected back toward the source. In addition, the speed of sound is slightly differ-ent in these different materials, so the time it takes for a reflec-tion to arrive back at the detec-tor depends on the material the reflection passes through. A computer is able to build an image based on the patterns of reflections detected.

Answer to Social Studies Activity

In addition to its well-known use in imaging the developing fetus in the uterus, ultrasound is also used in imaging other fluid-filled spaces in the body such as the kidney, heart, and bladder.

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