Post on 05-Jan-2016
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Waves Waves
Chapter 11 Section 1Chapter 11 Section 1
What is a What is a wavewave??
A A wavewave is a is a repeating disturbance repeating disturbance or movement that transfers or movement that transfers energyenergy through matter or space through matter or space
Waves transfer Waves transfer energyenergy NOT NOT mattermatter
MediumMedium: : the matter through which a the matter through which a wave travelswave travels; ; i.e. water, airi.e. water, air
Motion of a Duck on a WaveMotion of a Duck on a Wave
Water WaveWater Wave
Mechanical WavesMechanical Waves
Waves that can travel only through Waves that can travel only through mattermatter
There are There are two typestwo types::Transverse wavesTransverse waves (water, and (water, and
some seismic waves)some seismic waves)Longitudinal wavesLongitudinal waves (sound, spring)(sound, spring)
Requires a medium!!!!!!!Requires a medium!!!!!!!
Longitudinal (compressional) WavesLongitudinal (compressional) WavesParticles in the medium move parallel to Particles in the medium move parallel to
the direction of the waves.the direction of the waves.
particle motion
wave motion
The dense areas are called compressions.The less dense areas are rarefactions.
Transverse WavesTransverse WavesParticles in the medium move perpendicular to the Particles in the medium move perpendicular to the
direction of the waves. direction of the waves.
particlemotion
wave motion
Parts of a WaveParts of a WaveCrest:Crest: the highest point (top) of a the highest point (top) of a
transverse wave.transverse wave.Trough:Trough: the lowest point (bottom)the lowest point (bottom) of a of a
transverse wave. transverse wave.Wavelength:Wavelength: the distance from any point the distance from any point
on a wave to the same point on the next on a wave to the same point on the next wavewave. . (ex: crest to crest)(ex: crest to crest)
Amplitude:Amplitude: the height measured from the the height measured from the resting position.resting position.
trough
amplitude
crest
Parts of a WaveParts of a Wave
wavelength
Seismic WavesSeismic Waves
Seismic wavesSeismic waves are a are a combination of combination of compressional and transverse wavescompressional and transverse waves
1. They can travel along the earth’s 1. They can travel along the earth’s surfacesurface
2.2. When objects on the Earth’s surface When objects on the Earth’s surface absorb some of the energy carried by absorb some of the energy carried by seismic waves, they move and shakeseismic waves, they move and shake
Compressional
Transverse
AMPLITUDEAMPLITUDEMeasures the amount ofMeasures the amount of
energyenergy in a wave in a wave. .
Greater amplitude = Greater amplitude = more energymore energy..
FREQUENCYFREQUENCYThe rate at which waves pass The rate at which waves pass (the (the
# of full wavelengths that pass a # of full wavelengths that pass a point in one second).point in one second).
Symbol: Symbol: ff
Unit: Unit: Hertz (Hz)Hertz (Hz)
1 Hertz = 1 Hertz = 1 vibration per second1 vibration per second
Frequency is Frequency is 1 / T1 / T
WAVE SPEEDWAVE SPEEDHow fast a wave moves. How fast a wave moves.
Symbol: Symbol: vv Unit: Unit: m/sm/s
Wave speed is determined by the Wave speed is determined by the mediummedium.. Generally, waves pass Generally, waves pass through through solidssolids faster b/c particles faster b/c particles are closer and can pass vibrations are closer and can pass vibrations to each other more quickly.to each other more quickly.
Wave speed = frequency times wavelengthWave speed = frequency times wavelength
v = f v = f ·· λλ f = v / f = v / λλ
λλ = v / f = v / f
UNITS: UNITS: λλ = meters (m) = meters (m)
f = Hertz (Hz)f = Hertz (Hz)
v = m/sv = m/s
EQUATIONSEQUATIONS
v
f λ
The string of a piano that produces the note The string of a piano that produces the note middle C vibrates with a frequency of 264 Hz. middle C vibrates with a frequency of 264 Hz. If the sound waves produces have a If the sound waves produces have a wavelength of 1.30 m in air, what is the wavelength of 1.30 m in air, what is the speed of sound in air?speed of sound in air?f = 264 Hzf = 264 Hz
λλ = 1.30 m = 1.30 m
v = ?v = ?
v = 264 Hz (1.30 m)v = 264 Hz (1.30 m)
v = f · λ
v = 343.2 m/s
A water wave has a speed of 1.3 m/s. A A water wave has a speed of 1.3 m/s. A person sitting on a pier observes that it takes person sitting on a pier observes that it takes 1.2 s for a full wavelength to pass the edge of 1.2 s for a full wavelength to pass the edge of the pier. What is the wavelength of the water the pier. What is the wavelength of the water wave?wave?v = 1.3 m/sv = 1.3 m/sT = 1.2 sT = 1.2 sf f = 1 / T = 1 / 1.2 s = 1 / T = 1 / 1.2 s
= 0.83 Hz= 0.83 Hzλλ = ? = ?
λλ = 1.3 m/s / 0.83 Hz = 1.3 m/s / 0.83 Hz
λ = v / f
λ = 1.57 m