This quantity is related to the number of particles times mean polarizability by the Lorentz-Lorenz equation. This quantity can be negative in left-handed metamaterials. This quantity changes linearly (-5[1])in response to an electric field in Pockels effect, and it changes quadratically with the electric field in the Kerr effect. Taking the arctangent of the ratio of two (10[1])values of this quantity gives Brewster’s angle. The ratio of two values of this quantity equals the ratio of the sines of two angles in Snell's law. (10[1])For 10 points, dividing the speed of light by the speed of light in a medium gives what (10[1])quantity (10[1]-5[1])that measures (-5[1])how much light bends (10[1])in a medium? ■END■ (10[2]0[1])