Normal line

Definition

The normal line is an imaginary line perpendicular (at 90 degrees) to a surface at any given point. It serves as reference for measuring angles during reflection and refraction.

Related terms

Angle of incidence:

The angle between the incident ray and the normal line.

Angle of reflection:

The angle between the reflected ray and the normal line.

Angle of refraction:

The angle between the refracted ray and the normal line.