A light ray is incident normally on the face AB of a right-angled prism ABC (μ = 1.50) as shown in figure (18-E9). What is the largest angle ϕ for which the light ray is totally reflected at the surface AC?
Refractive index of glass prism
=1.50
Critical angle =
According to Snell’s law;
From figure, for total internal reflection, 
The largest angle ϕ for which the light ray is totally reflected at the surface AC =
1