Snell's law of refraction is the relationship between the angles of incidence and refraction with respect to the refraction indices of two different media. Snell's law of refraction can be applied to the refraction light for any two media. Snell's law predicts the angle of refraction that light follows when passing from one medium and into the next medium.
The formula for Snell's law of refraction is sine of theta of the first medium divided by sine of theta of the second medium equal to the velocity of the first medium (v1) divided by the velocity of the second medium (v2) equal to the refractive index of the second medium (n2) divided by the refractive index of the first medium (n1). Standard algebraic methods are used to solve this formula.
Theta represents the angle. Typically, the angle of light refraction through the first medium is known and the Snell's law of refraction formula is used to determine the angle of light refraction entering into the second medium.
Every medium has a specific refractive index that represents the factor by which the speed of light decreases when passing through the medium. Water, glass and air are the most common media that refract light.