Question

A ray of light strikes a plane mirror PQ at an angle of 20⁰, gets reflected and then strikes a second mirror QR placed perpendicular to the first mirror. What is the angle of reflection at the second mirror?

Answer 1

as we know , angle of incidence is equal to angle of reflection .

so the light ray from first mirror get reflected at an angle of 20° from the normal .

Forming a triangle from the incident ray on second mirror , amd the normals of mirror one and two . we apply the sum of all angle of a triangle is 180° .

we get 70° as the answer.