||It has been suggested that this article be merged with Clausius–Mossotti relation. (Discuss) Proposed since April 2016.|
The Lorentz–Lorenz equation, also known as the Clausius–Mossotti relation and Maxwell's formula, relates the refractive index of a substance to its polarizability. Named after Hendrik Antoon Lorentz and Ludvig Lorenz.
The most general form of the Lorentz–Lorenz equation is
When the polarizibility is small (such that |n-1| << 1) the equation reduces to:
This applies to gasses at ordinary pressures. The refractive index of the gas can then be expressed in terms of the molar refractivity as:
where is the pressure of the gas, is the universal gas constant, and is the (absolute) temperature, which together determine the number density .
The Lorentz–Lorenz equation is named after the Danish mathematician and scientist Ludvig Lorenz, who published it in 1869, and the Dutch physicist Hendrik Lorentz, who discovered it independently in 1878.