When both the permittivity and permeability of a material are negative, this quantity unusually takes a negative value.
When this value is expressed as a complex number, its imaginary part is known as the extinction coefficient. The change in this quantity due to an applied electric field is shown in the Kerr effect. When both the permittivity and permeability of a material are negative, this quantity unusually takes a negative value. Brewster's angle is given by the arctangent of the ratio of this quantity for two different materials. Two values of this quantity are multiplied by the sines of angles in Snell's Law. This quantity is equal to 1.33 in water and 1 in a vacuum. For 10 points, name this dimensionless quantity that is the ratio of the speed of light in a vacuum to that in another material, symbolized n.
When this value is expressed as a complex number, its imaginary part is known as the extinction coefficient.
index of refraction [or refractive index; prompt on n before it is read]