John William DraperBorn 5 May 1811; died 4 Jan 1882 at age 70. English-American chemist who pioneered in photochemistry. He recognized that light initiated chemical reactions as molecules absorbed light energy. The Draper Point is the name given to the point at which all substances glow a dull red (about 525 degrees C.). He described the effect of rise in temperature as the addition of more and more of the visible light region produced a white glow (1847). His interest in spectroscopy and photography was applied to give the first astronomical photograph. Its subject was the moon (1840). He also studied photographs of the solar spectrum to show that contained both infrared and ultraviolet light. His photographs of persons include the oldest surviving photographic portrait (1840), and he was one of the first to produce microphotographs. |
