Drude model

Summary

The Drude model, proposed by Paul Drude in 1900, describes electrical conduction in metals. In it, free electrons are accelerated by the electric field and lose their momentum in random collisions. It gives Ohm's law with an explicit conductivity, and a frequency-dependent conductivity and permittivity. It explains why metals reflect light below the plasma frequency and become transparent above it. In optics it is the limit of the Lorentz oscillator model without a restoring force.