This phenomena can be described by setting the ratio of the sines of the angles equal to the inverse of the ratio of this phenomena's namesake indices.
The Kerr effect changes the namesake ratio involved in this phenomena in the presence of an electric field. The lensmaker's equation relates one over the focal length to the focal lengths and the ratio of the values associated with this phenomena for the lens and the environment. This phenomena can be described by setting the ratio of the sines of the angles equal to the inverse of the ratio of this phenomena's namesake indices. That description is known as Snell's law. This is caused by the change of the velocity of a wave as it enters a new medium. For 10 points, name this phenomena that makes light bend when it enters water.
The Kerr effect changes the namesake ratio involved in this phenomena in the presence of an electric field.
{refraction}