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Heat and SoundWaves and Sound
1
Types of Waves
Harmonic Waves
Sound and Light Waves
Superposition and Interference
The Doppler Effect
Resonance
Heat and SoundWaves and Sound
2
Waves can be transverseFor example: Light waves, water waves and waves on a string...
Waves can be longitudinalFor example: Some seismic waves and sound waves…
Please, be patient. It takes awhile for the animations to start.
Heat and SoundWaves and Sound
3
Waves in Time
Waves are like many springs oscillating in time.
They have a period (T),a frequency (f) andan amplitude (A).
t
T
f = 1/T
Heat and SoundWaves and Sound
4
Waves in Space
Waves also oscillate in space.
They have a wavelength anda speed.
Heat and SoundWaves and Sound
5
Sound is a longitudinal wave
It travels through any gas, solid or liquid as a variation in pressure.
It has a speed that depends on the material (medium) that it travels through.
It has a wavelength and a frequency that determine the pitch.
It has an amplitude that determines the volume.
Heat and SoundWaves and Sound
6
Light is a transverse wave
It travels through vacuum as a variation in electric and magnetic fields.
It has a speed that never changes.
c = 3 x 108 meters/second
It has a wavelength and a frequency that determine the color.
It has an amplitude that determines the intensity.
Heat and SoundWaves and Sound
7
Transverse waves oscillate perpendicular to the direction of propagation.
Properties:
wavelengthamplitudespeedpropagation directionpolarization
Heat and SoundWaves and Sound
8
t
T
f = 1/T
Each point on a transverse wave oscillates perpendicular to the direction of propagation.
Properties:
periodfrequencyamplitudepolarization
Heat and SoundWaves and Sound
9
Properties:
wavelengthspeedpropagation direction
λ
y
x
v
Longitudinal waves oscillate parallel to the direction of propagation.
Heat and SoundWaves and Sound
10
Each point on a longitudinal wave oscillates parallel to the direction of propagation.
Properties:
periodfrequencyamplitude
t
T
f = 1/Tx
A
Heat and SoundWaves and Sound
11
λ
y
x
v
Properties:
wavelengthspeedpropagation directionperiodfrequencyamplitude
PitchDensity (of medium)LocationPitchPitchVolume
Sound is a longitudinal wave It travels through any gas, solid or liquid as a variation in pressure.
It has a speed that depends on the material (medium) that it travels through.
Heat and SoundWaves and Sound
12
Constructive interference occurs when both waves have the same phase.
Destructive interference occurs when both waves have opposite phase.
Definition of interference
y
xphase
Heat and SoundWaves and Sound
13
The frequency of sound changes depending on whether you move toward or away from the object emitting the sound
v is the velocity of the observer with respect to the source.
vs is the velocity of the sound.
v is positive if the observer is moving toward the source and negative if the observer is moving away from the source.
http://webphysics.ph.msstate.edu/jc/library/15-6/index.html
fv
vf
s
1
Heat and SoundWaves and Sound
14
For pipes the wavelength of a wave must fit within the length of the pipe.
Other waves can only be made by force.
...3,2,1 ;2
nn
L
Note Frequency
Middle C 261.7
D 293.7
E 329.7
F 349.2
G 392
A 440
B 493.9
C 523.3Speed of sound in air is343 meters/second = f x λ