Question

​ ​three plane mirrors are placed such that the angle between the first and the second or the second and third is the same θ. A light striking thr first mirror after reflection at the three mirrors emerges opposite to the inital direction. Find the value of θ ​ 60˚ 150˚ 120˚ 45˚

Answer 1

see diagram.

the angle between mirrors = t.
angle of incidence of light ray on the first mirror = x.

then x + t = 180 deg,  it is reflected from the third mirror , opposite to the initial ray.

Answer 2

Answer:

120

Explanation:

here t+x=180

t=x/2

180-t=t/2

360-2t=t

3t=360

t=120