An electromagnetic wave of wavelength `lamda_(0)` (in vacuum) passes from P towards Q crossing three difference media of refractive index `mu,2mu` and `3mu` respectively as shown in figure `phi_(P)` and `phi_(Q)` be the phase of the wave at points P and Q. Find the phase difference `phi_(Q)-phi_(P)`. [take `mu=1`]

Options

A. (a) `0`
B. (b) `pi/4`
C. (c) `pi/2`
D. (d) `pi`

Answer

C

Explanation

Optical path difference between (OPD) P and Q
`(O.P.D.)=2.25lambda_0xx1+(3.5lambda_0)xx2+3lambda_0xx3`
`=18.25lambda_0`
and phase difference `Deltaphi=(2pi)/(lambda_0)xxDeltax=pi/2`