…the fact or phenomenon of light, radio waves, etc. being deflected in passing obliquely through the interface between one medium and another or through a medium of varying density…
…division of a single incident light ray or other electromagnetic wave into two separate rays in an anisotropic medium…
…the refraction of elastic waves on passing between formations of rock having different seismic velocities…
…the angle made by a refracted ray with a perpendicular to the refracting surface…
