Question

. A ray of light is reflected by two
parallel mirrors (1) and (2) at points A and B.
The ray makes an angle of 25° with the axis
of the two mirrors
a) What is the angle of reflection at the point
of incidence A?
b) What is the angle of reflection at the point
of incidence B?
​

Answer 1

Given:

A ray of light is reflected by two parallel mirrors (1) and (2) at points A and B. The ray makes an angle of 25° with the axis  of the two mirrors .

To Find:

a) What is the angle of reflection at the point  of incidence A?

b) What is the angle of reflection at the point  of incidence B?

Solution:

given,

ray of light makes an angle of 25 degree with the axis of the two mirrors,

(a) here, $\angle i = 90-25=75 \ degree$

Hence, 75 degree is angle of reflection at the point of incidence A.

(b) here, it is given that, the two mirrors are parallel and AB intersect both of them , hence angle r and i are alternate interior angle and therefore equal in size.

Also, from law of reflection,

$i=r$

hence, $\angle i' = \angle r=\angle i = 75$ degree at the point of incidence B.