Iridescence

Iridescence, the sheen of mother-of-pearl and other objects possessing a finely-grooved surface. It is due to Interference (q.v.) between the waves of white light reflected from different levels in the grooving; some of the wave-lengths are more completely abolished by interference than others are; the result is that the residual vibration which reaches the eye contains a preponderant proportion of the rays which have been less affected by interference, and the reflected light accordingly presents colours which vary according to the angle of reflection.