Stefan, Josef(yō`zĕf shtĕf`än), 1835–93, Austrian physicist. At the Univ. of Vienna he became a professor of physics and later director of the Physical Institute. From his observations on the relationship between radiant heat emitted by a body and its temperature, Stefan concluded that the total radiation of a body was proportional to the fourth power of its absolute temperature. One of his students, Austrian physicist Ludwig Boltzmann, later derived the same relationship from a thermodynamic viewpoint. This principle, called the Stefan-Boltzmann law, played an important part in considerations leading to Max Planck's quantum theory.
Born Mar. 24,1835, in St. Peter, near the city of Klagenfurt; died Jan. 7, 1893, in Vienna. Austrian physicist. Member of the Vienna Academy of Sciences (1865).
Stefan studied at the University of Vienna from 1853 to 1858. He became an instructor in a private Realschule in Vienna in 1858 and a professor at the University of Vienna in 1863.
In 1879, Stefan showed experimentally that the energy radiated by a heated body is proportional to the fourth power of the body’s absolute temperature (the Stefan-Boltzmann law). Stefan also worked in such areas as optics, the physics of heat, capillarity, diffusion, and electromagnetic phenomena.