A light ray is incident normally on the face AB of a right-angled prism `ABC (mu==1.50)` as shown in figure. What is the largest angle `phi` for which the light ray is totally reflected at the surface AC ?

Answer

A, B, C

Explanation

Let `theta_c` be the critical angle for the glass,
`(sintheta_c)/sin90^@)=1/x`
`rarr sinthetac=1/1.5=2/3`
`rarr thetac=sin^-1 2/3`
for total interN/Al reflection `90^@=varphigttheta_c`
`rarr thetalt90^@=theta_c`
`rarr thetaltcos^-1(2/3)`
so the largest angle for which light is totally reflected at the surface is `cos^-1(2/3)`