A water film is formed on a glass block . A light ray is incident on water film from air at an angle `60^(@)` . What is the angle of incidence on the glass block ?
(Refractive index of glass = 1.5 , Refractive index of water = 4/3)

Options

A. `sin^(-1) ((2)/(sqrt3))`
B. `sin^(-1) ((8)/(sqrt3))`
C. `sin^(-1) ((sqrt3)/(4))`
D. `sin^(-1) ((3sqrt3)/(8))`

Answer

D

Explanation

For the ray travelling from air to water ,
`""_(a) n_(w) = (4)/(3) = (sin i)/(sin r)`
`therefore sin r = (sin 60^(@))/((4)/(3)) = (sqrt3)/(2) xx (3)/(4) = (3 sqrt3)/(8)`
`therefore r = sin^(-1) ((3sqrt3)/(8))`
The angle r in water is the angle of incidence (i) of the glass block .
`i =sin^(-1) ((3sqrt3)/(8))`