Interference is the addition (
superposition) of two or more
waves that results in a new wave pattern. As most commonly used, the term 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. Two non-
monochromatic waves are only fully
coherent with each other if they both have exactly the same range of
wavelengths and the same
phase differences at each of the constituent wavelengths.
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