What is the angle of incidence?

The angle of incidence is defined as the angle formed between the incident ray (the incoming light ray) and the normal line to the surface at the point of incidence. The normal is an imaginary line that is perpendicular to the surface at that point. This is a critical concept in optics, as it helps to determine how light behaves when it encounters different surfaces, such as reflective or refractive materials.

In the context of the other options, the angle between the incident ray and the reflected ray refers to the angle created after the light bounces off a surface, which is not the definition of the angle of incidence. The angle between the reflected ray and the normal describes another relationship that involves light post-reflection. Lastly, the angle at which light enters a material describes the concept of refraction but does not specify the relationship between the incoming light and the normal line as the angle of incidence does. Thus, the correct understanding of the angle of incidence is fundamental to analyzing how light interacts with different surfaces.