1. Refraction and Snell's Law

You may recall that waves change speed when they pass from one medium into another - their frequency stays the same but their wavelength changes. This in turn cause a change in their direction as one side of the wavefront slows down or speeds up before the other.

 

2. EM Wavespeed and Refractive Index

A little bit about little c and how this is related to the refractive index of a material.

 

3. Refraction Extra Points

A little bit extra on how as the wave speed changes this affects the wavelength and frequency of the wave.