Question

Two coherent sources of light interfere and produce fringe pattern on a screen. For central maximum, the phase difference between the two waves will be,

(1) $\pi$/2

(2) Zero

(3) $\pi$

(4) 3$\pi$/2

Answer 1

Ans: (2) Zero

Sol. For central maximum, path difference is zero hence phase difference for coherent sources of light will be zero. 

$∵ \phi={2\pi\over\lambda}\Delta x$

where $\Delta$x is path difference and $\phi$ is phase difference.