Wave Interference

When several waves are in the same location , the waves combine to produce a single new wave that is different from the

original wave.

1) Constructive Interference: when two waves interact and the resultant wave has a

larger amplitude (Part A, Figure below)

2) Destructive Interference: when two waves interact and the resultant wave has a smaller

amplitude (Part B, Figure below)

INTERFERENCE IN LIGHT WAVES: (transverse electromagnetic)

• Create colorful displays• Ex- soap bubbles- pg 476– You see many colors because the light is bouncing

off different parts of the bubble (creating differing wavelengths)

– These waves interfere constructively in some places and destructively in others.

– These different frequencies are interpreted by your eyes to create many different colors .

INTERFERENCE IN LIGHT WAVES: (transverse)

INTERFERENCE IN SOUND WAVES: (longitudinal mechanical)

• If two waves are “out of sync” they cause “beats” of louder noise (when they are in line and have constructive interference) and then quiet (when they are opposite and destructive interference occurs)

• http://library.thinkquest.org/19537/Physics5.html

STANDING WAVES:

• Form when a wave is reflected at the boundary of a medium. – Interference of the original wave with the reflected

wave causes the medium to vibrate in a stationary pattern that resembles a series of loops.

– The wave appears to be standing still, but it is not!!! (actually moving in both directions)

• NODES- – Lie at points where the crests of the original waves meet

the trough of the reflected waves, causing complete destructive interference.

• ANTINODES-– Midway between the nodes lie points of maximum

vibration – This is where the crests of both waves meet creating

complete constructive interference.

• http://paws.kettering.edu/~drussell/Demos/superposition/superposition.html