Physics: Reflection and Refraction of Light

Light ray

A directed line showing the path along which light travels, represented in ray diagrams by a solid straight line with an arrow pointing in the direction of propagation.

Light beam

A stream or collection of light composed of a set of light rays.

Parallel beam

A light beam consisting of rays that run equidistant and parallel to each other, such as rays originating from a point on a very distant object.

Divergent beam

A light beam consisting of rays that spread outward in different directions from a common point or light source.

Convergent beam

A light beam consisting of rays that approach each other and intersect at a single focal point.

Normal (Optics)

An imaginary line constructed perpendicular ($90^\theta$ or $90^\times$) to a reflecting or refracting surface at the exact point where a light ray strikes it.

Angle of incidence ($i$)