Ch. 14 - Waves & Sound

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