# Snell's Law - Refraction Calculator

To update the calculator, change the values in the colored boxes.

Angle of incidence (θi) =
Angle of refraction (θr) =
Critical angle = none
Medium one (i)
refractive index (ni) =
Medium two (r)
refractive index (nr) =
Speed = 2.9979e8 ms-1
Speed = 1.9986e8 ms-1
Normal
Interface

The angle of refraction of a light ray passing through an interface between two media is a function of the angle of incidence and the refractive indexes of the media.
sin θi
sin θr
=
nr
ni
Where:
θr = the angle of refraction
θi = the angle of incidence
ni = the refraction index of medium containing the incident ray
nr = the refraction index of medium containing the transmitted ray

There is no critical angle when the refractive index of the medium containing the incident ray is less than the medium with the transmitted ray.

Try the Snell's Law - refraction practice problems to test your understanding of the calculations

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