What is the angle called at which incoming light rays approach a surface?

The angle at which incoming light rays approach a surface is termed the angle of incidence. This angle is defined as the angle between the incident ray (the incoming light) and the normal line, which is an imaginary line perpendicular to the surface at the point of incidence. Understanding the angle of incidence is crucial in the study of optics, as it plays a significant role in various phenomena including reflection and refraction of light.

In the context of this question, the angle of reflection refers to the angle at which light reflects off a surface, which occurs after the light has already interacted with the surface. The angle of refraction pertains to the angle that describes how light bends as it enters a different medium; this angle is determined by Snell's law and the properties of the two media involved. The critical angle is specific to situations where light travels from a denser to a less dense medium and is related to total internal reflection. Thus, the angle of incidence is the appropriate term for the angle at which light approaches the surface.