Heat and SoundWaves and Sound

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Types of Waves

Harmonic Waves

Sound and Light Waves

Superposition and Interference

The Doppler Effect

Resonance

Heat and SoundWaves and Sound

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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

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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

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Waves in Space

Waves also oscillate in space.

They have a wavelength anda speed.

Heat and SoundWaves and Sound

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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

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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

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Transverse waves oscillate perpendicular to the direction of propagation.

Properties:

wavelengthamplitudespeedpropagation directionpolarization

Heat and SoundWaves and Sound

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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

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Properties:

wavelengthspeedpropagation direction

λ

y

x

v

Longitudinal waves oscillate parallel to the direction of propagation.

Heat and SoundWaves and Sound

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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

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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

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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

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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

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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