what is a ray

In math, a ray is a part of a line that has a fixed starting point but no endpoint, and it can extend infinitely in one direction. A ray is named using its initial point and any other point through which it passes. Rays are a fundamental building block of math, and they can be used to form different angles depending on how they are arranged. Two rays can create an angle, and multiple angles can create a polygon. In optics, a ray is an idealized geometrical model of light or other electromagnetic radiation, obtained by choosing a curve that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow. Rays in homogeneous media are straight, but they bend at the interface between two dissimilar media and may be curved in a medium in which the refractive index changes. Geometric optics describes how rays propagate through an optical system.