Light of wavelength `5000 Å` is travelling in air. A thin glass plate (mu=1.5) of thickness `1 mm` is placed in the path of light. The change in phase of light is

Options

A. zero
B. `pi//2`
C. `pi`
D. `(3pi)//2`

Answer

A

Explanation

`Deltax=(mu-1)t=(1.5-1)xx10^(-3)=5xx10^(-4)m`
`phi=(2pi)/lambda Deltax=(2pi)/(5xx10^(-7))xx5xx10^(-4)=2000pi`
`2000 pi i.e. 0`