A ray of light incident paralled to the base $\mathrm{PQ}$ of an isosceles right-angled triangular prism PQR suffers two successive total internal reflections at the faces $P Q$ and QR before emerging reversed in direction as shown
If the refractive index of the material of the prism is $\mu$, then

• Correct answer
  A

  $\mu>\sqrt{5}$
• B

  $\sqrt{3} < \mu < \sqrt{5}$
• C

  $\sqrt{2} < \mu < \sqrt{5}$
• D

  $\mu < \sqrt{2}$

Solution

also $\begin{array}{ll} & 45+r>C \\ & 45-r>C \\ & 90>C \\ & \because \mu>\sqrt{2}\end{array}$

Hence, the correct answer is option: 'A'.