Question

Light enters an isosceles right triangular prism at normal incidence through face $AB$ and undergoes total internal reflection at face $BC$ as shown below.
The minimum value of the refractive 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 $1.42$

The reflection angle is 45 ,that is also critical angle

now $\mu sin\theta =1\to \mu =\sqrt{2}=1.42$