Snell's Law (related to indices of refraction)
Description
Snell’s law (also known as the Snell–Descartes law and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass and air. Snell’s law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the reciprocal of the ratio of the indices of refraction. 
Variables
| θ1 | Angle of incidence (degree) |
| θ2 | Angle of refraction (degree) |
| n2 | Refractive index of second medium (refraction) (dimensionless) |
| n1 | Refractive index of first medium (incidence) (dimensionless) |