Question

Two plane mirrors are inclined at 70°. A ray incident on one mirror at angle θ after reflection falls on second mirror and is reflected from there parallel to first mirror. The value of θ is(a) 50°(b) 45°(c) 30°(d) 55°

Answer 1

b.45 degrees is the answer I guess

Answer 2

Answer:

a) 50°

Explanation:

Angle of inclination = 70°

Let θ = b

Angle of incidence = b = reflection angle.

Considering the angles formed by the reflected rays and two mirrors in the triangle will be -

Angle between the reflected ray and the mirror (2nd) = b+20.

Angle of incidence on the second mirror = 90 - [180- 70 - (90-b) ] = 70 - b

Since, it is parallel to the 1st mirror : b+20 = 70

= b = 70-20

= b = 50

Thus, the value of theta = 50°