Question

In fig. AB is a mirror , PQ is incident ray and QR the reflected ray.

Answer 1

Heya!

Since anglePQA (i) = angleRQB(r),

By linear pair,

i + r + 100 = 180...........
i + r = 180 - 100 = 80.......

But, i = r

...........thus........

2i = 80.....
i = r = 80/2 = 40..........

Therefore, angle PQA = 40 degree............

Answer 2

pq is a incident ray, qr is reflected ray
you read that ,in laws of reflection , ，<i=<r
i+r+100=180 ( linear pair
i+r=180-100=80
i=r
80/2=40
pqa is 40