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

We know that angle of incident ray is equal to angle of reflected ray.
⇒ ∠𝑖= ∠𝑟
But it is given that
∠𝑖+ ∠𝑟=90°
⇒∠𝑖+ ∠𝑖=90°
⇒2∠𝑖=90°
⇒∠𝑖=90°/2
⇒∠𝑖=45°