Question

two plane mirrors are inclined at 70 deg. a ray incident on on one mirror at angle theta, after reflection falls on second mirror and is reflected from there parallel to the first mirror. What is theta

Answer 1

theta = 50 degrees

Solution:
angle of incidence = reflection angle.
so,
angle of incidence = 90 - [180- 70 - (90-b) ]
= 70 - b
reflection angle = b+20.

b+20 = 70
b= 70-20
b=50 degrees