Lorentz Lorenz Equation

A relation between the polarizability of a molecule and the refractive index n of a substance made up of molecules with this polarizability. The Lorentz-Lorenz equation can be written in the form
= (3/4N) [(n2-1/(n2 + 2)]
, where N is the number of molecules per unit volume. The equation provides a link between a microscopic quantity (the polarizability) and a macroscopic quantity (the refractive index). It was derived using macroscopic electrostatics in 1880 by H. A. Lorentz and independently by the Danish physicist Ludwig Valentin Lorenz also in 1880. Compare Clausius-Mossotti equation.