TOPIC 3: WAVE BEHAVIOR

Waves The behavior of a wave is greatly influenced by the medium in

which it is traveling.

The wave frequency remains unchanged in different medium. The velocity of a wave depends upon the medium. Since the velocity is changed, the wavelength is also changed.

A. Reflection

When a wave comes in contact with an obstacle or the boundary of its medium a reflection will occur.

Part of the wave returns in the direction it was traveling. The displacement is inverted.

A. Reflection

When the wave pulse hits a fixed boundary (a wall) the wave is reflected back.

Incoming waves are known as incident waves.

A. Reflection If the wave is reaches the boundary for its medium

and is entering a new medium (air to water, or air to object, etc.): Part of the wave is reflected back Part of the wave is transmitted to the new

medium

Remember that the wave frequency remains constant, the velocity and the wavelength are changed.

A. Reflection

The Law of Reflection states that the angle of the incident wave and the reflected wave are the same. (more to do with light!)

B. Interference Waves are a transfer of energy. More than

one wave can occupy the same space at the same time.

When this happens interference occurs.

B. Interference

Principle of superposition: The displacement of the medium of the region where two waves meet (often referred to as the overlap region) can be determined by the algebraic sum of the individual wave’s displacement.

B. Interference

2 types of Interference: Constructive: The two waves are in phase. The

resulting wave is larger than the individual waves.

Destructive: The two waves are out of phase and the resulting wave is smaller than the individual waves.

B. Interference

Constructive:

Amplitude increases!

B. Interference

Destructive: Amplitude drops!

B. Interference

The type of interference that occurs depends upon the displacement of the original waves and the phase that the waves are in when they overlap.

C. Refraction

When a transmitted wave enters a new medium the direction at which it travels in may change.

A new medium will alter the velocity and direction (slightly) of the wave.

C. Refraction

The law of refraction: The velocity of the incident wave and the initial angle at which it was traveling is related to and can be used to determine the angle and speed of the transmitted wave.

2 represents the refracted wave. 1 represents the incident wave.

Sinθ2/sinθ1 = v2/v1

D. Diffraction

Waves spread out as the travel in three dimensions. When they encounter an obstacle they bend around it.

D. Diffraction

The amount of diffraction depends upon the wavelength and the size of the obstacle.

If the wavelength is larger than the object there will be a large diffraction pattern.

If the object is much larger than the wave then there will be little diffraction.