Question
Light enters an isosceles right triangular prism at normal incidence through face $A B$ and undergoes total internal reflection at face $B C$ as shown below.The minimum value of the refractive index of the prism is close to
✓
Answer
(c)
As total internal reflection occurs at angle of incidence, $i=45^{\circ}$.'
So, using $\mu=\frac{1}{\sin C}$, we have
$\mu=\frac{1}{\sin 45^{\circ}}=\sqrt{2} \text { or } \mu \approx 1.42$
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