The angle of incidence dictates how light interacts with a boundary between two materials. It is measured from the incoming ray to a line strictly perpendicular to the surface, not to the surface itself. This angle determines the proportion of light that will be reflected, refracted, or absorbed based on the optical properties of the medium.
Heard on the job
At a high angle of incidence, most of the beam skips off the glass instead of passing through it.
Do not mix it up with
- Angle of reflection: Incidence is the incoming angle, while reflection is the outgoing bouncing angle.
Related terms
Angle of reflection
The angle measured between a reflected light ray and the surface normal.
Angle of refraction
The angle between a refracted light ray and the normal line as it passes through a new medium.
Grazing
Lighting a surface from a very steep angle, close to the wall, to bring out its texture with strong highlights and shadows.