brainpop

http://www.brainpop.com/science/energy/waves/

http://www.brainpop.com/science/energy/waves/

Wave: A traveling disturbance that carries energy through matter and/or space. Waves move through material…they do not move the material

• Need a vibration as a sourceVibration: source of all waves; particles moving• Any movement that follows the same path

repeatedly. gives rise to a wave. Medium: the matter or substance ( s, l, g ), through

which a wave is transmitted. Ex: air-gas; water –liquids, glass-solids

The parts of a wave:• CREST: The highest point of a wave.

• Trough: the lowest point of a wave.

What are the 3 major characteristics of waves?

amplitude, wavelength and frequency.Wavelength:the distance between 2 consecutive crests or troughs ( crest to crest or trough to trough)

Amplitude: maximum movement from rest. It shows the energy of the wave!Height of the wave( rest to crest; rest to trough)

Frequency: the # of complete waves, or cycles, per second. Higher frequency= more energy

crest and trough = 1 wave

Hertz: unit used to measure freq.

Higher the energy, the higher the freq-

Ex:

Diagram of a Wave- pg. 4

Amplitude

rest

Frequency = crest to trough– How many are there?

2 types of waves :

1. Transverse: particles move perpendicular to the direction of the wave propagation

2.Longitudinal: particles move in the same direction of

the wave propagation ..ex: sound waves

rarefaction rarefaction

longitudinal

transverse

• Transverse and longitudinal waves can combine to form surface waves.

• These are how water waves are formed

Mechanical waves: waves that require a medium Ex: sound waves, water waves, slinky waves and rope waves Electromagnetic waves: waves that do NOT require a medium- can move thru space. Ex: light waves, microwaves, radio waves, visible light

NOT ALL WAVES NEED A MEDIUM(SOLID, LIQUID OR GAS)

HAVE 2 CATEGORIES :

TYPE OF WAVE:

Ex: light wavesEx: sound wavesEx: rope, slinky , water waves

Transverse, waves, transverse, Needs a medium, mechanical, Does not need a medium, electromagnetic, longitudinal,

DO NOW

mechanical electromagnetic

Ex: sound waves Ex: light waves

waves

HAVE 2 CATEGORIES :

NEEDS A:medium

DOES NOT NEED A:medium:

TYPE OF WAVE:

longitudinal transverse transverse

Ex: rope, slinky, Water waves

HomeworkCheck :

://studyjams.scholastic.com/studyjams/jams/science/weather-and-climate/waves-and-currents.htm

• Slinky and rope demo

Light

• Light is an electromagnetic (EM) wave. An electromagnetic wave is a wave that travels as vibrating electric and magnetic fields.

• EM waves do not require medium to travel through.

• EM waves are produced by the vibration of electrically charged particles.

Study jams on light

• http://studyjams.scholastic.com/studyjams/jams/science/energy-light-sound/light-absorb-reflect-refract.htm

Wave bounce back after striking a barrier during reflection.

Angle of incidence

Angle of reflection

A. Of incidence = A. of reflection

Barrier

Th

e n

orm

al

.

Wave Refraction

• The straw looks “bent” in the water

Refraction is the bending of a wave when it passes at an angle from one medium to another.

Diffraction

• Waves bend around barriers or through openings during diffraction.

• Radio waves are most often used for communication.

• Microwaves are used for cooking and in radar.

• Infrared waves have shorter wavelengths and higher frequencies than microwaves. The absorption of infrared waves is felt as an increase in temperature.

• Visible light is the very narrow range of wavelengths that humans can see. Different wavelengths are seen as different colors.

• Ultraviolet light is useful for killing bacteria and for producing vitamin D in the body, but overexposure can cause health problems.

• X rays and gamma rays are EM waves that are often used in medicine. Overexposure to these EM waves can damage or kill living cells.

• Highest energy is gamma ray, with shortest wavelength

What is sound?Sound Wave- The energy produced by a sound, which emanates outward as a wave in all directions, and is carried by matter, such as air.

Sound can also travel through water, glass and metals.

Anything that vibrates produces sound.Sound waves require a medium.

Study jams on Sound

Study Jams

Sound• Waves that require a medium are called

mechanical waves.• Sound waves are mechanical waves.• All sounds are created by vibrations and travel

as longitudinal waves.

Frequency

A description of sound known as high or low is the frequency of the sound.

Frequency units - Hertz1 Hz= to 1 wave or cycle per second.

Fill in on your sound sheet• Infrasonic: below 20 Hz ( frequency )• Ultrasonic: above 20,000 Hz ( frequency )• Add: Humans hear from 20 – 20 000 Hz (frequency)• Add: SW need a medium• Add: Speed of sound: fastest in a solid, depends on

the medium, and is affected by: a) temperature, b) density and c) elasticity.• Echo: reflected SW• Sonar /ultrasound: reflected SW• Add: As Amplitude increases, intensity of sound

increases, which makes sounds louder.

Sound waves above frequencies of 20,000 are called : Ultrasonic, b/c they are above range of Human Hearing. Ex: dogs, bats, cats, dolphins

Humans hear from 20-20,000 Hz.

Infrasonic: sound waves below 20 Hz-below range of human hearing.

Ex: elephants

Echoes are reflected sound waves.

Some animals use echolocation to find food or navigate around objects. Sonar and ultrasonography are types of echolocation. They reflect sound waves !

• Sound waves travel in all directions away from their source.

Decibel scale – 0- 130 dB ( loudness)

The doppler effect

When there is a motion between the source of a sound and its receiver,( the person) the Doppler Effect occurs. THE CHANGE IN FREQUENCY OF A WAVE, CAUSES THE DOPPLER EFFECT !

EX: Driving in a car past a police siren or an ambulance

• The Doppler Effect is the apparent change in frequency of a sound caused by the motion of either the listener or the source of the sound.

Speed of sound is determined by the Temperature, elasticity and density of the medium through which the sound travels through. In general, it travels fastest through solids !

Sound travels slower at a lower temperature, and faster at a higher temperature.

For elasticity, solids are most elastic, liquids next elastic and gases the least elastic-therefore the poorest transmitters of sound

• The speed of sound depends on the medium through which the sound is travelling. Changes in temperature of the medium can affect the speed of sound.

• Avg. speed of sound in air at 68 deg. F is about 340 m/s

STOP

Loudness is related to the amount of energycarried by a wave. How much energy is carried by the wave in a certain amount of time is called the INTENSITY of the wave.

Intensity determines the loudness of sound.Measured in decibels( dB).

The larger the amplitude, the greater the intensity, the higher the dB.

Frequencies measured in Hz; Intensity measured in dB.

PITCH• The pitch of a sound depends on frequency. • High-frequency sounds are high-pitched, and low-

frequency sounds are low-pitched.• Humans can hear sounds with frequencies between

20 Hz and 20,000 Hz.Highest Pitch

Lowest Pitch

• The intensity of a sound increases as the amplitude increases.

• Loudness is affected by intensity(amplitude), and is expressed in decibels.

• An oscilloscope can be used to “see” sounds.

When you speak, your vocal cords vibrate.

When they move inward, the air between them is pushed together(compressed).

when they move outward, there is less air in that area, so fewer particles are there (rarefaction).

Let’s do pages 5 and 7 together:

now, page 9 : Then , get a ruler each, and draw the angle of reflection at the same angle as the angle of incidence ( incoming light wave ), but in the opposite side and direction….

Now: we are ready to do a small lab on: reflection, refraction and diffraction…..

Wave Interference

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

• Amplitude increases during constructive interference and decreases during destructive interference.

What increased?

What decreased?

amplitude

Wave Diffraction

• Standing waves are waves in which portions of the wave do not move and other portions move with a large amplitude.

Sample Calculation• Calculate the speed of a wave that has a

frequency of 3 waves per second and a wavelength of .5 m

• 3-Step Answer– 1. ν = λ x f– 2. f = 3 waves/sec (Hz)

ν = ? λ = .5 m

– 3. ν = .5 m x 3 waves/sec

ν = 1.5 m/sec

Wave Calculations• The speed that a wave can travel depends on

the media it travels through– Ex: The speed of sound through air is 340 m/s, but

through steel it is 5200 m/s.

• The speed that waves are traveling can be calculated.

• Formula for calculating wave speed: ν = λ x f– v = speed– λ = wavelength– f = frequency

• The sounds you hear are converted into electrical impulses by your ears and then sent to your brain for interpretation.

• Exposure to loud sounds can cause hearing loss and tinnitus.

http://science360.gov/obj/tkn-video/f06b3ba0-6b5f-4e00-a821-6d97dc67ed68

• The speed of light (and all other EM waves) in a vacuum is 300,000,000 m/s.

• All EM waves travel at the speed of light. • EM waves differ only by wavelength and

frequency.• The entire range of EM waves is called the

electromagnetic spectrum.

• http://phet.colorado.edu/en/simulation/bending-lighthttp://phet.colorado.edu/en/simulation/bending-light

PRODUCES THE UPSIDE DOWN IMAGEAND CONVERTS TO ELECTRICAL IMPULSES

The main function of the eye is to convert light from the outside world into electrical nerve impulses

PROTECTS THE EYE FROM DIRTAND BACTERIA

OPENING THRUWHICH LIGHT ENTERS

PATH FOR ELECTRIC IMPULSESFROM RETINA TO BRAIN

LIGHT ENTERS AND IS FOCUSED .

MUSCLE THAT CONTROLSAMOUNT OF LIGHT ENTERING EYE.

2.

1.

3.

6.

4.5

The eyeThe main function of the eye is to convert light from

the outside world into electrical nerve impulses