This entry contributed by Dana Romero
A phenomenon that occurs when certain transparent or translucent materials are subjected to external or internal stresses. The existing stress, which usually varies from point to point, causes local changes in the index of refraction. This in turn means variations in the speed of light through the material. When coming from a beam of polarized light, individual rays take different paths through the material and, upon recombining, produce interference patterns. Properly interpreted, lines of the same refringence indicate points in the material of the same stress. This is the principle that underlies the technique of photoelasticity.
Index of Refraction, Photoelasticity, Stress
