Question

(a) Why are coherent sources necessary to produce a sustained interference pattern? 

(b) In Young’s double slit experiment using mono-chromatic light of wavelength λ, the intensity of light at a point on the screen where path difference is λ, is K units. Find out the intensity of light at a point where path difference is 2λ/3.

Answer 1

(a) Coherent sources are needed to ensure that the positions of maxima and minima do not change with time.
(b) We know that