Question

The law of reflection states that the angle of incidence equals the angle of refraction. Define the angle of incidence in terms of a line normal to the surface.

Answer 1

I got it

Answer 2

First of all, the Law of Reflection states that the angle of incidence equals the angle of REFLECTION (refraction is totally different)!

A line "normal" to a surface is perpendicular to that surface. The angle of incidence and angle of reflection are both measured from the light ray itself to the normal line.