Find the thickness of a plate which will produce a change in optical path equal to half the wavelength `lamda` of the light passing through it normally. The refractive index of the plate is `mu`.

Options

A. `(lambda)/(4(mu-1))`
B. `(3lambda)/(4(mu-1))`
C. `(lambda)/((mu-1))`
D. `(lambda)/(2(mu-1))`

Answer

D

Explanation

From, `(mu-1)t=n lambda`, we get, `t=(n lambda)/((mu-1))`
when, `n lambda=(lambda)/(2)" then " t=(lambda)/(2(mu-1))`