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Two plane mirrors are inclined to each other at some angle. A ray of light incident at $30^{\circ}$ on one mirror after reflection from the other mirror retracts its path. The angle between the mirror is :

$(a)\;30^{\circ} \\ (b)\;45^{\circ} \\ (c)\;90^{\circ} \\ (d)\;20^{\circ} $

1 Answer

Angle of incidence = angle of reflection $=30^{\circ}$
Since ray $ED$ returns its path it must fall normally
$\therefore \angle EDB= 90^{\circ}$
$\therefore \angle EOD= 90^{\circ}-60^{\circ}$
$\qquad= 30^{\circ}$
Hence a is the correct answer.
answered Jan 15, 2014 by meena.p

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