In the ideal double-slit experiment, when a glass-plate(refractive index 1.5) of thickness t is introduced in the path of one of the interfering beams (wave-length `lamda`), the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass-plate is

Options

A. `2 lambda`
B. `2 lambda//3`
C. `lambda//3`
D. `lambda`

Answer

a

Explanation

Path difference `(mu - 1) t = n lambda`
For minimum t, `m = 1`
`:. t = 2 lambda`