Interference

Interference filter Newton’s ring

Optical Interference Optical interference corresponds to the superposition of two or more light waves yielding a resultant irradiance that deviates from the sum of component irradiance.

Light waves interfere with each other much like mechanical waves do All interference associated with light waves arises when the electromagnetic fields that constitute the individual waves combine LINEAR SUPERPOSITION!

Resultant

Irradiance

The phase difference arising from a combined path length and initial phase difference.

Total constructive interference For maximum irradiance

Total destructive interference For minimum irradiance

For I 1 =I 2

Photo shows an interference pattern by two holes

Moire Pattern

White Light Interference

Phase difference

Optical path difference

Conditions of Interference

Coherent Sources Constant phase difference Such sources may or may not be in step but are always marching together

Interference of light from two bulbs?

For random rapid nature of phase change

The resultant flux density arising from N sources having random, rapidly varying phases is given by N times the flux density of any one source.

In phase coherent sources For each amplitude E 01

1. Optics Author: Eugene Hecht Class no. 535 HEC/O Central library IIT KGP