Question

What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?

Answer 1

As per the laws of reflection 

The angle of incidence ∠i = angle of reflection ∠r 

Here as given ∠i + ∠r = 90° 

∴ ∠i + ∠i = 90 ° 

or ∠i = 90/2 = 45 ° 

Hence angle of incidence of a ray = 45 degree