Question

Two plane mirrors are inclined at an angle of theta. A ray of light is incident on one mirror at an angle of i. The ray is reflected from this mirrors , falls on the second mirror from where it is reflected parallel to the first mirror. What is the value of 'i' , the angle of incidence in term of theta.​

Answer 1

Answer:

The situation is illustrated in figures.XAis the incident ray.BCis the final reflected ray.it is given that BCis parallel to mirrorM1.Look at the assignment of the angles carefully .Now N2is normal to mirrorM2Therefore.

β=θ

Then fromΔOAB

θ+β+90∘−i=180∘

or θ+θ+90∘−i=180∘

or i=2θ−90∘

Thus if the angle of incidence is i=2θ−90∘,then the final reflected ray will be parallel to this first mirror.