Interference is the addition (superposition) of two or more waves that result in a new wave pattern.
Interference usually refers to the interaction of waves which are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
[center][img]http://upload.wikimedia.org/wikipedia/commons/2/2c/Two_sources_interference.gif[/img]
Animation of interference of waves coming from two point sources.[/center]
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