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

Find the thickness of a transparent plastic plate which will produce a

1.	Find the thickness of a transparent plastic plate which will produce a change in optical path equal to the wavelength lamda of the light passing through it normally, The refractive index of the plastic plate is mu.
Answer» Solution :When light travel a distance x in a medium of REFRACTIVE index `m`, its optical path `=MU x` change in optical path `=mu x-x =(mu-1) x`. this is to be EQUAL to `LAMDA`. But `(mu-1) x= lamda` The THICKNESS of the plate `x= lamda/(mu -1)`