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Physics 120 1
Wave Motion
Physics 120 2
Wave Motion
Physics 120 3
Wave Characteristics
Physics 120 4
Velocity of Waves
For all waves:
For a wave on a string or cord (stringinstruments):
2
Physics 120 5
Ch 11: Problem 38
(a) AM radio signals have frequenciesbetween 550 kHz and 1600 kHz and travelwith a speed of 3.00 x 108 m/s. What are thewavelengths of these signals?
(b) On FM, the frequencies range from 88.0MHz to 108 MHz and travel at the samespeed. What are their wavelengths?
Physics 120 6
Types of waves (11-8)
Transverse displacement is
perpendicular to velocity Ex - light
Longitudinal displacement is parallel
to velocity Ex - sound
Physics 120 7
Energy Transport in Waves (11-9)
Energy is proportional to A2
Intensity, I
Physics 120 8
Reflection & Transmission (11-11)
3
Physics 120 9
Reflection & Transmission
Physics 120 10
Wave Fronts & Rays
Wave fronts connects peaks
Ray perpendicular to wave
front shows direction of motion
Physics 120 11
Reflection of plane waves
Law of reflection: angle of incidence = angle of reflection angle measured from normal
Physics 120 12
Interference;Principle of Superposition (11-12)
DestructiveInterference
ConstructiveInterference
PartialDestructiveInterference
4
Physics 120 13
Standing Waves; Resonance (11-13)
wheren = 1,2,3,...
Physics 120 14
Ch 11: Problem 52
If a violin string vibrates at 440 Hz as itsfundamental frequency, what are thefrequencies of the first four harmonics?
Physics 120 15
Refraction (11-14)
Physics 120 16
Diffraction (11-15)
When waves encounter an obstacle, theybend around it somewhat.
Amount ofdiffraction
wavelength ofwave
size of openingor obstacle
5
Physics 120 17
Think-Pair-Share
Ch 11: Problem 72 When you walk with a cup of coffee (diameter 8
cm) at just the right pace of about 1 step persecond, the coffee sloshes more and more untileventually it starts to spill over the top. Estimatethe speed of the waves in coffee.
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