What willl be the minimum angle of incidence such that the total internal reflection occurs on both the surfaces? `

Answer

C

Explanation

For total internal reflection on interface AB
`sini=(1)/(`_2^1mu)=(1mu)/(2mu)=(sqrt2)/(2)=(1)/(sqrt2)impliesi=45^circ`
For total internal reflection in interface CD.
`sini=(1)/(`_2^3mu)=(3mu)/(2mu)=(sqrt3)/(2)impliesi=60^circ` `implies` The minimum angle for total internal reflection for both the interface is `60circ`.