1. The angle between a ray that is refracted at a surface between two different media and the perpendicular (normal) to the surface at the point of refraction.
2. The angle between a wavefront and a surface at which it has been refracted.
Geology and Earth Sciences
The angle between a refracted ray or wave and the normal to a refracting surface. The angle of refraction is related to the angle of incidence by Snell’s law. A ray or wave entering a medium in which its speed is higher than in the medium it is leaving will deviate away from the normal, whereas when it enters a medium of lower speed it will deviate towards the normal.