$(a)\;30^{\circ} \\ (b)\;90^{\circ} \\ (c)\;60^{\circ} \\ (d)\;20^{\circ} $

Applying Snell's law

$1 \sin 60^{\circ}= \sqrt 3 \sin r$

$\qquad => r =30^{\circ}$

From symmetry $r'=r=30^{\circ}$

Again applying snell's law at second surface $1 \sin e =\sqrt 3 \sin r$

$=> e=60^{\circ}$

Deviation at first surface $=i-r=60^{\circ}-30^{\circ}= 30^{\circ}$

Deviation at second surface $=e-r=60^{\circ}-30^{\circ}= 30^{\circ}$

$\therefore $ total deviation $=60^{\circ}$

Hence c is the correct answer.

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