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 (wavelength `lambda`), 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 // 3) lambda`
C. `lambda//3`
D. `lambda`

Answer

a

Explanation

If after placing the plate, intensity at the position of central maxima position remains unchanged, then it means first maxima takes position of central maxima, In case of minimum thickness of plate, 2 path difference created by the plates should be equal to `lambda`.
i.e., `t (mu - 1) = lambda`
`t ((3)/(2) - 1) = lambda implies t =2 lambda`