Named after Willebrord Snell (1591 - 1626).
Snells law defines the angle of refraction of a light beam when it passes from one medium to another. If the second refractive index (nb) is higher than the first (na) then the beam bends towards the normal, otherwise it bends away from it.
- In the curved atmosphere, Snell's law becomes
- R = distance from the local centre of curvature
See also: Angle of Reflection.