Ernst Ruhmer
German physicist (1878–1913)
Ernst Walter Ruhmer (15 April 1878 – 8 April 1913) was a German physicist. He was best known for investigating practical applications making use of the light-sensitivity properties of selenium, which he employed in developing wireless telephony using line-of-sight optical transmissions, sound-on-film audio recording, and television transmissions over wires.
Career
Ruhmer's father was an inventor and manufacturer. From 1897 to 1900 he studied mathematics and natural sciences in Berlin, and the next year continued his studies in Giessen. His early work included extensive research in developing selenium cells that were more sensitive, and faster reacting, to the effects of light illumination. In December 1902 he and Salomon Kalischer were issued German patent 151,971 for their method of producing photographic images by exposing electrically conductive selenium-coated plates. Ruhmer also designed a light-sensitive control switch, using a selenium cell, which was successfully used to automatically turn off the flow of a buoy's illuminating gas during daylight hours. In 1904 he established a private physics laboratory, located in southwest Berlin.
Wireless telephony
Photophone
Ruhmer first gained widespread recognition for his work on improvements to Alexander Graham Bell's optical wireless telephone, the photophone. Bell introduced this device in 1880, which used selenium cells in the receiver to convert the fluctuating light produced by the transmitting unit into sounds.
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