The locus of points where adjacent light rays intersect after reflecting off a curved surface or passing through a lens. It represents the brightest region of a focused beam in a single plane, often appearing as a sharp cusp shape where intensity spikes.
Heard on the job
The ray trace shows a distinct caustic curve near the focal point of the spherical mirror.
Related terms
Caustic
The bright envelope of light rays formed when a beam is reflected or refracted by a curved surface.
Caustic surface
The three-dimensional envelope of concentrated light rays formed by reflection or refraction.
Spherical aberration
An optical defect where light rays passing through the edge of a lens focus at a different point than central rays.