A plane mirror is placed horizontally inside water (`mu`=4/3). A ray falls normally on it. Then mirror is rotated through an angle `theta`. The minimum value of `theta` for which ray does not come out of the water surface is

Options

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

Answer

C

Explanation

(c ) The reflected ray will rotate by angle 2`theta`. For TIR to take place at water-air boundary,
`sin2thetagtsintheta_(C)orsin2thetagt1/mu`
`thereforethetagt1/2sin^(-1)(3/4)`