Two smooth reflecting boards are placed making an angle of with each other

PHYSICS · Single correct · CBSE · Physics · Sound · Sound

Problem

Two smooth reflecting boards are placed making an angle of

60^{\circ}

with each other. A narrow beam of sound strikes the first board with an angle of incidence of

20^{\circ}

and then gets reflected from the second board. What is the angle between the final beam and the original incident beam after the two reflections? (a)

80^{\circ}

(b)

60^{\circ}

(c)

120^{\circ}

(d)

140^{\circ}