Refractive index of one of the two media in which the light beam propagates. In vacuum, \( n_1 = 1 \).
Refractive index of the second medium into which the light beam is refracted.
Angle of incidence from the incident beam in the first medium. Measured relative to the normal (a line perpendicular to the surface).
Angle of refraction of the incident beam in the second medium. Measured relative to the normal.