Wave TheoryEssential Question: What is a wave?

Answer Me!!! Give an example of a wave. Then describe

what that wave carries.

Waves A wave is produced by an oscillation

(vibration) of the medium (material) surrounding the wave source.

Waves transfer energy. They do NOT transfer mass (or material).

Stop and Think… Take 1 minute to discuss with a neighbor how

energy can be transferred through a medium without transferring any matter.

Amplitude Amplitude (A) is the height of the wave from

rest position. The more energy a wave has the larger its

amplitude.

amplitude

Wavelength Wavelength is the length of the wave, or

the distance between identical points in the wave form.

Wavelength ()

Frequency Frequency (f) is the number of waves that

pass a point in one second. Frequency is measured in Hertz (Hz) or

cycles/second.

0

5

10

15

20

0 2 4 6 8

Time

Practice Problem

A

B

C

Order the three waves from lowest frequency to highest frequency.

Period The period of a wave is the amount of time needed

for that wave to complete one cycle. Period can be determined by the following:

fT

1

Stop and Think… What does the amplitude of different waves

(i.e: water waves, light waves, sound waves) represent?

What does the frequency of these waves represent?

Answer Me!!!!! What is the significance of amplitude in the

following waves: Water Sound Light

Pulses and Period Waves A pulse is a single disturbance that moves

from one point to another.

A period wave is a repeating pattern of identical pulses.

Transverse Waves A transverse wave is a wave where the

particles vibrate perpendicular to the motion of the wave.

The top of a transverse wave is called the crest the bottom is called the trough.

Wave Motion

ParticleVibration

Longitudinal Waves A longitudinal wave is a wave where the

particles vibrate parallel to the motion of the wave. Sound waves are longitudinal waves.

Wave Motion

Particle vibration

Practice Problem 1 A transverse wave is moving with a velocity v

along a rope. In which direction will a knot in the rope move as the wave passes through it?

Reflection of Waves If a wave pulse is incident on (hits) a new medium, some of

that wave will be reflected, some will be transmitted into that new medium and some will be absorbed.

The wave will be reflected at the same angle that the wave struck the surface (measured from the normal).

Lightwave

Reflectedwave

Transmittedwave

AIR

WATER

Practice Problem 2 A physics student notices that 4 waves arrive

at the beach every 20 seconds. What is the frequency of these water waves?

Practice Problem 4

Determine the Amplitude, wavelength of this wave if each hash mark is 1 centimeter.

Phase Two points are in phase if they are the same

height above or below the rest position and moving in the same direction.

Two points are out of phase if they are not in phase.

Wave Velocity The velocity of a wave is a measure of how

quickly energy is transferred through the medium.

Wave velocity is directly related to both wavelength and frequency.

v = f

Practice Problem 6 A periodic transverse wave has an amplitude

of 0.20 m and a wavelength of 3.0 m. If the frequency of this wave is 12 Hz, what is its speed?

Practice Problem 7 Orange light has a frequency of 5.0 x 1014 Hz

in a vacuum. What is the wavelength of this light?

Practice Problem 8 A surfacing whale produces water wave crests

having an amplitude of 1.2 m every 0.40 seconds. If the water wave travels at 4.5 m/s, what is the wavelength of the wave?

Practice Problem 9 Determine the frequency of a ray of light with

a wavelength of 6.21 x 10-7 m.