In figure, if a parallel beam of white light is incident on the plane of the slit, then the distance of the nearest white spot on the screen form O is [assume `d lt lt D, lambda lt lt D`]

Options

A. 0
B. d/2
C. d/3
D. d/6

Answer

D

Explanation

let the distance 'y' from 'O' where nearest white spot occurs. Then the path difference=0
`impliesqrt(D^(2)+((2d)/(3)-y)^(2))-sqrt(D^(2)+((d)/(3)+y)^(2))=0`
`thereforey=(d)/(6)`