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Ch. 14 - Waves & Sound
I. Characteristics of Waves Waves Transverse waves Longitudinal waves Measuring waves
A. Waves
Wavesrhythmic disturbances that carry energy through
matter or space
Mediummaterial through which a wave transfers energysolid, liquid, gas, or combinationelectromagnetic waves don’t need a medium
(e.g. visible light)
A. Waves
Two Types:
Longitudinal Transverse
B. Transverse Waves
Transverse Wavesmedium moves
perpendicular to the direction of wave motion
B. Transverse Waves
Wave Anatomy
crests
troughswavelength
wavelength
amplitude
amplitude
corresponds to the amount of
energy carried by the wave
nodes
C. Longitudinal Waves
Longitudinal Waves (a.k.a. compressional)medium moves in the same direction as wave
motion
C. Longitudinal Waves
Wave Anatomy
rarefaction
compression
wavelength
wavelength
Amount of compression corresponds to amount of energy AMPLITUDE.
D. Measuring Waves
Frequency ( f )
# of waves passing a point in 1 second
Hertz (Hz)shorter wavelength
higher frequency higher energy
1 second
D. Measuring Waves
Velocity ( v )speed of a wave as it moves forwarddepends on wave type and medium
v = × f v: velocity (m/s)
: wavelength (m)
f: frequency (Hz)
Sonic Boom: occurs when a jet flies
faster than the speed of sound due to compressions waves that stack up until the molecules in the wave
explode away from the source.
http://youtu.be/gWGLAAYdbbc
Doppler Effect
As an ambulance comes toward you, the wavelengths are compressed in front of the ambulance (shorter wavelength leads to higher pitch).
http://www.youtube.com/watch?v=imoxDcn2Sgo
http://youtu.be/h4OnBYrbCjY
Doppler Effect diagram
Words associated with waves that you should
know:
http://youtu.be/mh3o8gUu4AE
15 minute video
Standing Wave
Occurs when there is continuous interference of equal but opposite
amplitude. The wave appears to be standing still.
http://youtu.be/RUpjYDteYcg
https://www.youtube.com/watch?v=18BL7MKjtZM
WORK:v = × f
v = (3.2 m)(0.60 Hz)
v = 1.92 m/s
D. Measuring Waves
EX: Find the velocity of a wave in a wave pool if its wavelength is 3.2 m and its frequency is 0.60 Hz.
GIVEN:
v = ?
= 3.2 m
f = 0.60 Hz
v
f
WORK: f = v ÷
f = (5000 m/s) ÷ (417 m)
f = 12 Hz
D. Measuring Waves
EX: An earthquake produces a wave that has a wavelength of 417 m and travels at 5000 m/s. What is its frequency?
GIVEN:
= 417 m
v = 5000 m/s
f = ?
v
f