In Euclidean geometry
, a ray
, or half-line
, given two distinct points
A (the origin) and B on the ray, is set of points C on the line
containing points A and B such that A is not strictly between C and B.
A B C
In geometric optics
is a curve describing the direction in which light
or other electromagnetic radiation
is propagated. The ray in geometric optics is perpendicular to the wavefront in physical optics.
In most simple cases, light rays within a given medium are straight lines.
Light passing from one medium to another undergoes refraction or total internal reflection following Snell's law.