Question

Light enters an isosceles right triangular prism at normal incidence through face $AB$ and undergoes total internal reflection at face $BC$ as shown in the diagram :
The minimum value of the reflective index of the prism is close to :

• A. $1.10$
• B. $1.55$
• C. $1.42$
• D. $1.72$

Answer 1

The correct option is C $1.42$

We know that

Incident angle given by

$i={45}^{\circ }\ge C$
$c={45}^{\circ }$ for minimum $\mu$

By using snells law we have
$\mu sin45=1$
$\mu =\sqrt{2}=1.42$