Question

A ray of light incidents normally on first face of the prism and the emergent ray grazes the second surface. If $A$ is the angle of the prism and $C$ is its critical angle then the correct choice is:

• A. $A$
• B. $A>C$
• C. $A=C$
• D. $A\ge C$

Answer 1

Answer: (C)

$A=C$

When the ray is incident on first face normally, then the angle of incidence on second face is A by geometry, as shown.

Since question says that this condition meets the critical condition for total internal reflection, A = C

Answer. C) A=C