Drude, Paul Karl Ludwig (12.07.1863–5.07.1906) was a German physicist and a member of the Berlin Academy of Sciences (1905). Born in Braunschweig. Graduated from the University of Göttingen (1887), where he worked. In 1894–1900 he was professor at the University of Leipzig, in 1901–05 at the university in Giessen, and from 1905 at the University of Berlin.
His work was in the field of optics, electromagnetic waves, electron theory and the physics of metals. He developed a theory of the polarisation of light reflected from a metal surface and a theory of the dispersion of light, was the first to detect and explain the anomalous dispersion of the permittivity, and worked out methods of measuring the permittivity. Independently of J. J. Thomson he laid (1900) the foundations of the classical electron theory of metals. According to his theory of conductivity (the Drude theory), the electric current in metals is carried by free electrons whose behaviour is analogous to that of an assembly of molecules of an ideal gas. This conception of an “electron gas” in metals enabled Drude to explain a number of experimental regularities, in particular the Wiedemann–Franz effect, and also the contact potential difference, thermionic emission and others, and to find the electrical conductivity coefficient of metals.
He was the editor of the journal “Annalen der Physik” (from 1900).