Question

if the light ray falls normally on a plane mirror then what is the angle of incidence?​

Answer 1

Answer: In such cases, ∠i = 0°.

Explanation: Falling normally means that the incident light ray falls perpendicular to the point of incidence. So, angle between incident ray and normal = 0° (angle of incidence).

More: In such cases, angle of deviation (δ) is always 180°. [∵ δ = 180° - (∠i + ∠r) = 180°.]