A plate of thickness t made of a material of refractive index `mu` is placed in front of one of the slits in a double slit experiment. (a) Find the changes in he optical path due to introduction of the plate. (b) Wht should be the minimum thickness t which will make the intensity at the centre of the fringe pattern zero ? Wavelength of the light used is `lamda`. Neglect any absorption of light in the plate.

Answer

A, B, D

Explanation

a. Change in the optical path `=mut-t`
`=(mu-1)t`
b. to have should shift by one half a fringe.
`(mu-1)t=lamda/2`
`rarr t=lamda/(2(mu-1))`