For 10 points, name this phenomenon in which a wave changes direction as it passes from one medium to another.
The negative type of this phenomenon can be found in left-handed materials whose permittivity and permeability are both less than zero. Birefringence is sometimes known as the "double" type of this phenomenon. Its namesake law, which is often written as n-one times the sine of theta-one equals n-two times the sine of theta-two, is better known as Snell's law. For 10 points, name this phenomenon in which a wave changes direction as it passes from one medium to another.
The negative type of this phenomenon can be found in left-handed materials whose permittivity and permeability are both less than zero.
{refraction}