Question

Two plane mirrors are inclined at an angle tita.It is found that a ray incident on one mirror at any angle is randered parallel to itself after reflection from both the mirrors.Find the value of tita

Answer 1

Let θ be the angle between two mirrors OM1 and along BC the angle of reflection is α

From figure we have ∠M1BA=∠OBC=∠M1OM2=θ

Similarly for reflection at mirror OM2, we have ∠M2CD=∠BCO=∠M2OM1=θ

Now in triangle OBC

3θ=180

∴θ=60∘

Hence b is the correct answer.