WavesWavesPart II: BehaviorPart II: Behavior

The Wave Machinehttp://www.cbu.edu/~jvarrian/applets/waves2/simwav_g.htm

Standing WavesStanding Waves• Standing waves are a result of interference.Standing waves are a result of interference.

– Combination of incident and reflected wavesCombination of incident and reflected waves• Two waves of equal amplitude and wavelength Two waves of equal amplitude and wavelength

pass in opposite directions. pass in opposite directions. • Node – stationary point where waves are always Node – stationary point where waves are always

out of phase.out of phase.• Antinode – largest point of amplitudeAntinode – largest point of amplitude

Standing WavesStanding WavesDue to interference

Nodes “out of Phase”

Antinodes “In phase”

Interference - waves combineInterference - waves combine

Destructive or Constructive Destructive or Constructive InterferenceInterference

http://users.erols.com/renau/wave_interference.html

Principle of SuperpositionPrinciple of Superposition

• When two or more waves meet, there is When two or more waves meet, there is interference.interference.

• The displacement caused by two or more The displacement caused by two or more waves is the algebraic sum of the individual waves is the algebraic sum of the individual waveswaves

• Constructive interference – waves in phase Constructive interference – waves in phase addadd

• Destructive interference – waves out of Destructive interference – waves out of phase subtractphase subtract

ReflectionReflection• When wave reaches When wave reaches

a barrier at least a barrier at least part of the wave part of the wave bounces back.bounces back.

• Angle of incidence Angle of incidence equals the angle of equals the angle of reflectionreflection

• http://http://www.physicsclassroom.com/www.physicsclassroom.com/mmedia/waves/fix.htmlmmedia/waves/fix.html

Change in MediaChange in Media• A place where the substance the wave is A place where the substance the wave is

traveling through changestraveling through changes• Example: A light wave traveling through air Example: A light wave traveling through air

passes through a glass windowpasses through a glass window• Some of wave is transmitted and some is Some of wave is transmitted and some is

reflectedreflected

RefractionRefraction• When a wave travels When a wave travels

in a different medium in a different medium the velocity changesthe velocity changes

• This change in This change in velocity results in velocity results in bending of the wave.bending of the wave.

• This is why a pencil This is why a pencil appears to bend in a appears to bend in a glass of water.glass of water.

DiffractionDiffraction• Waves normally Waves normally

travel in a straight travel in a straight line in a medium.line in a medium.

• When waves meet When waves meet a barrier, they bend a barrier, they bend around the edges.around the edges.

• This is called This is called diffraction.diffraction.

• http://www.control.co.kr/java1/http://www.control.co.kr/java1/masong/oneslit.htmlmasong/oneslit.html

http://library.thinkquest.org/19537/java/Doppler.htmlhttp://www.control.co.kr/java1/masong/doppler.html

The Doppler EffectThe Doppler Effect• The apparent The apparent

change in change in frequency of a frequency of a wave due to the wave due to the motion of the motion of the source or receiver. source or receiver.

• Greater speeds Greater speeds produce greater produce greater effects.effects.

Doppler effect - ExamplesDoppler effect - Examples• car horncar horn• sirenssirens• radar gunradar gun• lightlight

– increase frequency – blue shiftincrease frequency – blue shift– decrease frequency – red shiftdecrease frequency – red shift