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# The refractive index of a prism is 2. This prism can have a maximum refracting angle of

$(a)\;90^{\circ} \\ (b)\;60^{\circ} \\ (c)\;45^{\circ} \\ (d)\;30^{\circ}$

Critical angle $\theta_c=\sin ^{-1} \bigg(\large\frac{1}{\mu}\bigg)$
$\qquad= \sin ^{-1} \bigg(\large\frac{1}{2} \bigg)$
$\qquad= 30^{\circ}$
The angles made by the ray inside the prism canot be greater than$30^{\circ}$
A= $r_1+r_2$
if $A > 60$, the ray does not emerge from prism.
So maximum refracting angle can be $60^{\circ}$
Hence b is the correct answer.

edited Jul 23, 2014