(a) Write the conditions under which light sources can be said to be coherent. (b) Why is it necessary to have coherent sources in order to produce an interference pattern ?

(a) Write the conditions under which light sources can be said to be c

1.	(a) Write the conditions under which light sources can be said to be coherent. (b) Why is it necessary to have coherent sources in order to produce an interference pattern ?
Answer» Solution :(a) Following two CONDITIONS are necessary for light sources to be coherent: (i) The sources must emit light of same wavelength (or same frequency). (ii) The originating PHASE difference between light waves emitted by the sources should be either zero or have a constant value. (b) In order to produce an interference PATTERN the light sources must be coherent one so that the interference pattern obtained on the screen is a sustained pattern and positions of bright and dark fringes do not change with TIME.

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(a) Write the conditions under which light sources can be said to be coherent. (b) Why is it necessary to have coherent sources in order to produce an interference pattern ?

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