born Feb. 22, 1857, Hamburg, Ger.
died Jan. 1, 1894, Bonn
German physicist.
While a professor at Karlsruhe Polytechnic (1885–89), he produced electromagnetic waves in the laboratory and measured their length and velocity. He showed that the nature of their vibration and their susceptibility to reflection and refraction were the same as those of light waves, and he proved that light and heat are electromagnetic radiations. He was the first to broadcast and receive radio waves. In 1889 he was appointed professor at the University of Bonn, where he continued his research on the discharge of electricity in rarefied gases. The hertz (Hz), a unit of frequency in cycles per second, is named for him.