Ray (optics)

Objects to be imaged are treated as collections of independent point sources, each producing spherical wavefronts and corresponding outward rays.

The ray in geometrical optics is an abstraction useful for approximating the paths along which light propagates under certain circumstances.

The simplifying assumptions of geometrical optics include that light rays: In physics, ray tracing is a method for calculating the path of waves or particles through a system with regions of varying propagation velocity, absorption characteristics, and reflecting surfaces.

For example, ray-marching involves repeatedly advancing idealized narrow beams called rays through the medium by discrete amounts.

When applied to problems of electromagnetic radiation, ray tracing often relies on approximate solutions to Maxwell's equations such as geometric optics, that are valid as long as the light waves propagate through and around objects whose dimensions are much greater than the light's wavelength.

Rays and wavefronts
Diagram of rays at a surface, where is the angle of incidence , is the angle of reflection , and is the angle of refraction
Single lens imaging with the aperture stop. The entrance pupil is an image of the aperture stop formed by the optics in the front of it, and the location and size of the pupil are determined by chief rays and marginal rays, respectively.
The exit pupil is the image of the aperture stop formed by the optics behind it, and the location and size of the pupil are determined by chief rays and marginal rays.