The plane at which the incident ray, reflected ray, and normal lie is called the plane of incidence.

Here's a breakdown:

* Incident ray: The ray of light that strikes a surface.

* Reflected ray: The ray of light that bounces off the surface.

* Normal: An imaginary line perpendicular to the surface at the point of incidence.

The plane of incidence is essential for understanding the laws of reflection, which state:

1. The angle of incidence is equal to the angle of reflection. These angles are measured between the incident/reflected ray and the normal.

2. The incident ray, reflected ray, and normal all lie in the same plane. This is the plane of incidence.