Physics

Problem

Two plane mirrors

M_1

and

M_2

are fixed perpendicular to each other. A light ray strikes

M_1

making an angle of

30^{\circ}

with the mirror surface, reflects, falls on

M_2

, and reflects again. The angle between the initial incident ray and the final emergent ray is a)

120^{\circ}

180^{\circ}

90^{\circ}

150^{\circ}