State any three conditions for a sustained interference of light waves.

Explanation

For a sustained interference of two light waves,
(i) Both the sources should be identical (same amplitude and frequency).
(ii) Both the sources should be coherent (same phase or phase difference between the two waves).
(iii) Both the waves should travel in the same direction and interfere at small angles.
(iv) Both the sources should be separated by only a small distance.
(v) Both the sources should be of narrow thickness.