refractan

Refractan is a term used in optics education to denote a hypothetical material employed to illustrate the behavior of light at interfaces, refraction, and related optical phenomena. It is commonly introduced in teaching contexts to help students visualize how light changes speed and direction when crossing boundaries.

In practice, refractan has no standard chemical composition. Textbooks treat it as a transparent, non-absorbing or weakly dispersive material with a defined refractive index n that can be varied by scenario. The index may be assumed constant or modeled with a dispersion relation to simulate different wavelengths.

Because of its hypothetical status, refractan is used to demonstrate Snell's law, critical angle, total internal reflection, and gradient-index effects; it can be part of virtual labs or physical demonstrations using real substances chosen to approximate target indices. The concept allows educators to illustrate how refractive properties influence imaging, lens design, and optical interfaces without committing to a specific material.

Safety and handling are not defined for refractan as a single material; educators should consult actual material data sheets if a real analogue is used. The term refractan serves primarily as a pedagogical device rather than as a description of a concrete chemical substance.

See also: refractive index, Snell's law, gradient-index materials, immersion media.