Comparing the iridescent pattern of a soap-bubble with the also iridescent surface of a wafer it is obvious that both is caused by the same optical effect:the white-light-interference.Certain wavelengths of the visible light are either amplified or attenuated by the interferences of the reflected rays so that the surface reflects the light in different colors,depending on the film thickness.This effect can be used for the non-destructive and non-contacting film thickness measurement.
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