# Snell's Law

**Snell's Law** describes how the direction of light changes when it moves from one medium to another.
What Snell's Law says is that when light moves from a medium with a high index of refraction to a medium with a low index of refraction it will bend away the normal of the plane dividing the two media. Conversely, when light moves from a medium with a low index of refraction to a medium with a high index of refraction it will bend towards from the normal dividing the two media.

The two forms of the law are:

- n
_{1}sin(θ_{1}) = n_{2}sin(θ_{2}) - v
_{2}sin(θ_{1}) = v_{1}sin(θ_{2})

where:

- n
_{1}and n_{2}are the indices of refraction in media 1 and 2, respectively - v
_{1}and v_{2}are the velocities of light in media 1 and 2, and - θ
_{1}and θ_{2}are the angle from the normal of the plane dividing the 2 media and the ray.

The index of refraction of a material is inversely proportional to the speed of light in that material, i.e. light will move slower in a material with a high index of refraction than it will in a material with a low index of refraction.