Question

A ray of light strikes at an angle of 80 with respect to mirror. What is the angle of reflection?

Answer 1

Answer:

90

Explanation:

An angle of incidence of 90 ∘ is NOT normal incidence. Instead, 0 ∘ is normal incidence. When the wave is incident at 90 ∘ , it is travelling parallel to the interface. The easy answer is that since the angle of reflection equals angle of incidence, the reflected ray will also be at 90 ∘ . The longer answer is that 90 ∘ is an unrealistic angle of incidence because it is exactly parallel to the mirror. One could argue such a wave never reflects so there would be no reflected wave.

This problem of a wave travelling parallel to the interface is virtually impossible to handle numerically and virtually impossible to deal with experimentally. Devices behave very strangely and uncontrollably around this condition