Snell law

Refraction is the bending of the path of a light wave as it passes across the boundary separating two
media. Refraction is caused by the change in speed experienced by a wave when it changes medium.
Lesson 1, focused on the topics of "What causes refraction?" and "Which direction does light refract?" In
that lesson, we learned that light can either refract towards the normal (when slowing down while
crossing the boundary) or away from the normal (when speeding up while crossing the boundary). The
focus of Lesson 2 is upon the question of "By how much does light refract when it crosses a boundary?"
In the first part of Lesson 2, we learned that a comparison of the angle of refraction to the angle of
incidence provides a good measure of the refractive ability of any given boundary. The more that light
refracts, the bigger the difference between these two angles. In this part of Lesson 2, we will learn about
a mathematical equation relating these two angles and the indices of refraction of the two materials on
each side of the boundary.

Using Snell's Law to Predict An Angle Value
As with any equation in physics, the Snell's Law equation is valued for its predictive ability. If any three
of the four variables in the equation are known, the fourth variable can be predicted if appropriate
problem-solving skills are employed