Physical Science EOCT Physical Science EOCT ReviewReview

Domain IVDomain IVWaves, Electricity and Waves, Electricity and

MagnetismMagnetism

Parts of a WaveParts of a Wave

Mechanical (Longitudinal) Mechanical (Longitudinal) WavesWaves

Examples are sound waves and slinkys

Electromagnetic Waves Electromagnetic Waves (Transverse)(Transverse)

• Electromagnetic waves are Electromagnetic waves are transverse wavestransverse waveswhich have both an electric and and which have both an electric and and magnetic effect. magnetic effect.

• The energy of the photons is directly The energy of the photons is directly proportional to the frequency.proportional to the frequency.

LightLight

• Light is a form of electromagnetic radiation (EM)Light is a form of electromagnetic radiation (EM)

• EM spectrum shows the forms of radiation in EM spectrum shows the forms of radiation in order of increasing frequency (and energy) and order of increasing frequency (and energy) and decreasing wavelengthdecreasing wavelength

Color of LightColor of Light

• We see different colors depending on the We see different colors depending on the frequency of light emitted or reflectedfrequency of light emitted or reflected

• This is the reason blue flames are hotter This is the reason blue flames are hotter than yellow. Blue has a higher frequency so than yellow. Blue has a higher frequency so more energy.more energy.

Sample QuestionSample Question

• How are the frequency and wavelength How are the frequency and wavelength related to the energy carried by waves?related to the energy carried by waves?– Answer: Higher frequency waves have more Answer: Higher frequency waves have more

energy while longer wavelength waves energy while longer wavelength waves have less energy. Frequency and energy have less energy. Frequency and energy are directly related while wavelength and are directly related while wavelength and energy are inversely related. Radio waves energy are inversely related. Radio waves (long wavelength) have less energy than (long wavelength) have less energy than gamma waves (high frequency).gamma waves (high frequency).

Sample QuestionSample Question

• How are frequency and wavelength How are frequency and wavelength related?related?– Answer: Frequency and wavelength are Answer: Frequency and wavelength are

inversely related. High frequency waves inversely related. High frequency waves have short wavelengths.have short wavelengths.

Electromagnetic Wave (EM) Electromagnetic Wave (EM) versus versus Mechanical WaveMechanical Wave

EM WAVEEM WAVE

• does not require does not require matter to transfer matter to transfer energyenergy

• CANCAN travel through travel through a vacuuma vacuum

• example: lightexample: light

MECHANICAL MECHANICAL WAVEWAVE

• does require does require matter to transfer matter to transfer energyenergy

• CANNOTCANNOT travel travel through a vacuumthrough a vacuum

• example: soundexample: sound

Sample QuestionSample Question

• Make a Venn Diagram to Compare Make a Venn Diagram to Compare electromagnetic and mechanical electromagnetic and mechanical waves.waves.– Sample Answer: Electromagnetic waves Sample Answer: Electromagnetic waves

(light) do not require matter to transfer (light) do not require matter to transfer energy while mechanical waves (sound) energy while mechanical waves (sound) require matter to transfer energy. In require matter to transfer energy. In other words, EM waves will travel in a other words, EM waves will travel in a vacuum while mechanical waves will not.vacuum while mechanical waves will not.

Reflection of LightReflection of Light

• When light strikes a When light strikes a boundary, it reflects.boundary, it reflects.

• The angle at which the The angle at which the wave approaches a flat wave approaches a flat reflecting surface is reflecting surface is equal to the angle at equal to the angle at which the wave leaves which the wave leaves the surface (like a the surface (like a bounce pass of a bounce pass of a basketball).basketball).

• Reflection results in Reflection results in image formation. image formation.

DiffractionDiffraction

We say that the wave bends around the barrier, or that it

changes directions.  Where the wave was traveling in a straight line before passing the barrier, it

is now 'bent' or it changed direction after passing the barrier. DIFFRACTION of a wave is the

bending or redirection of the travel of the wave when it passes

a barrier without changing the medium in which the wave is

traveling.

Refraction of LightRefraction of Light• Light waves travel Light waves travel

faster in air than in faster in air than in water and slower in water and slower in glass than water.glass than water.

• More dense = More dense = slower lightslower light

• When light enters a When light enters a different medium, different medium, speed changes and speed changes and it bends.it bends.

• Bending of light Bending of light due to change in due to change in speed = speed = REFRACTIONREFRACTION

Sample QuestionSample Question

A. Reflection onlyB. Refraction onlyC. Both Reflection and

RefractionD. Neither Reflection or

Refraction

The correct answer is “C” because some

The light will be reflected some will be absorbed

And therefore refracted

Sound and mediumsSound and mediumsSound travels fastest through solids. This is because molecules in a solid medium are much closer together than those in a liquid or gas, allowing sound waves to travel more quickly through it. In fact, sound waves travel over 17 times faster through steel than through air. The exact speed of sound in steel is 5,960 meters per second (13,332 mph)! But, this is only for the majority of solids. The speed of sound in all solids are not faster than in all liquids.

Remember that Density is the key to how Fast it travels!

Wave InterferenceWave Interference

• the phenomenon the phenomenon which occurs when which occurs when two waves meet two waves meet while traveling along while traveling along the same medium the same medium

• constructiveconstructive = = waves add to produce waves add to produce a larger wavea larger wave

• destructivedestructive = waves = waves cancel to produce a cancel to produce a smaller wavesmaller wave

CONSTRUCTIVE

DESTRUCTIVE

The Doppler EffectThe Doppler Effect• observed observed

whenever the whenever the source of waves is source of waves is moving with moving with respect to an respect to an observer observer

• an apparent an apparent change in change in frequency occursfrequency occurs

• toward = higher toward = higher frequencyfrequency

• away = lower away = lower frequencyfrequency

ElectricityElectricity

• Electrons carry a negative charge.Electrons carry a negative charge.

• Lost electrons = positive chargeLost electrons = positive charge

• Gained electrons = negative chargeGained electrons = negative charge

• REMEMBER:REMEMBER:– Like charges repelLike charges repel– Opposites attractOpposites attract

Static ElectricityStatic Electricity

• 3 causes:3 causes:

• FrictionFriction

• ConductionConduction

• InductionInduction

If you charge a balloon by rubbing it on your hair, it picks up extra electrons and has a negative charge. Holding it near a neutral object will make the charges in that object move. If it is a conductor, many electrons move easily to the other side, as far from the balloon as possible. If it is an insulator, the electrons in the atoms and molecules can only move very slightly to one side, away from the balloon. In either case, there are more positive charges closer to the negative balloon. Opposites attract. The balloon sticks.

Electrical CircuitsElectrical Circuits

• Current flows in a Current flows in a closedclosed circuitcircuit

• Two types of Two types of circuits:circuits:– SeriesSeries (single path) (single path)– ParallelParallel (many (many

paths)paths)

SERIES

PARALLEL

2 types of electrical currents2 types of electrical currents

Direct current DCDirect current DC

• Means to move Means to move continuously in the continuously in the same directionsame direction

• Car Batteries is an Car Batteries is an exampleexample

Alternating Alternating Current ACCurrent AC

• have electrons that have electrons that can change can change directiondirection

• a gasoline-driven a gasoline-driven generator is an generator is an exampleexample

Ohm’s Law Relates current, voltage and resistance

Sample QuestionSample Question

The correct answer is “B”

ElectromagnetElectromagnet

• One can make an electromagnet with a nail, One can make an electromagnet with a nail, battery, and wirebattery, and wire

• When current flows through the coiled wire, the When current flows through the coiled wire, the nail becomes magnetized. The more wraps-the nail becomes magnetized. The more wraps-the greater the energy.greater the energy.

Electric GeneratorsElectric Generators

Faraday discovered that if an electric conductor, like a copper wire, is moved through a magnetic field, electric current will flow (be induced) in the conductor. So the mechanical energy of the moving wire is converted into the electric energy of the current that flows in the wire. This is called electromagnetic induction

Sample QuestionSample Question

The correct answer is “A”

Sample QuestionSample Question

•     When a loop of wire is turned in a magnetic field, electrical charges move through thewire, creating an electrical current. This is the basis for an electric generator, so answer Dis correct.

Figure ReferenceFigure Reference• Distance versus Time Graph figures: source unknown Distance versus Time Graph figures: source unknown • Forces figure: retrieved from Forces figure: retrieved from

http://www.glenbrook.k12.il.us/gbssci/phys/CLass/newtlahttp://www.glenbrook.k12.il.us/gbssci/phys/CLass/newtlaws/u2l2c1.gifws/u2l2c1.gif

• Determining the Net Force figure: retrieved from Determining the Net Force figure: retrieved from http://www.glenbrook.k12.il.us/gbssci/phys/CLass/newtlahttp://www.glenbrook.k12.il.us/gbssci/phys/CLass/newtlaws/u2l2d11.gif ws/u2l2d11.gif

• Newton’s Laws, Gravity, Work, Types of Mechanical Newton’s Laws, Gravity, Work, Types of Mechanical Energy, Conservation of Energy, Light, Interference, and Energy, Conservation of Energy, Light, Interference, and Doppler Effect figures: retrieved from Doppler Effect figures: retrieved from http://www.physicsclassroom.com http://www.physicsclassroom.com

• Electrical Circuits figures: retrieved from Electrical Circuits figures: retrieved from http://www.autoshop101.com/trainmodules/elec_circuits/chttp://www.autoshop101.com/trainmodules/elec_circuits/circ101.html irc101.html

• Electromagnet figure: source unknownElectromagnet figure: source unknown