7. when a wave crosses a surface at an angle from one medium into another, why does it change directions as it moves across the boundary into the new medium? use 3 – 4 complete sentences in your own words to explain.

The changing direction of light is called refraction. This happens because the medium that the wave is going into is either more dense or less dense than the medium the wave was in before. Depending on the density of the second medium, the wave will refract either closer or farther away from the normal (a verticle line in the middle in which you calculate the incident and refracted rays from). If the second medium is denser than the first medium, then the wave will move closer to the normal. If the second medium is less dense, then the wave will move away from the normal.