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# A ray of light strikes a material of refractive index $\mu= \sqrt 3$. If the reflected and refracted light are perpendicular to each other, what is the angle of incidence.

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

$\large\frac{\sin \theta }{\sin r} $$=\mu Now we have \angle r +90^{\circ} + \angle NOB =180^{\circ} \angle NOB =\angle \theta \therefore \angle =90^{\circ}-\theta \large\frac{\sin \theta}{\sin (90 -\theta)}$$= \sqrt 3$
$\large\frac{\sin \theta}{\cos \theta}$$=\sqrt 3$
$\tan \theta= \sqrt 3$
$\theta =60^{\circ}$
Hence c is the correct answer.