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:

<math>n_1 \sin{\theta_1} = n_2 \sin{\theta_2}</math>
<math>v_1 \sin{\theta_1} = v_2 \sin{\theta_2}</math>

where:

<math>n_1</math> and <math>n_2</math> are the indices of refraction in media 1 and 2, respectively

<math>v_1</math> and <math>v_2</math> are the speeds of light in media 1 and 2

<math>\theta_1</math> and <math>\theta_2</math> are the angles measured from the normal and the respective 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.