Helmholtz, Hermann Ludwig Ferdinand von
Helmholtz, Hermann Ludwig Ferdinand von (1821-1894), a German physiologist and physicist. He was the first to put into mathematical form the law of conservation of energy (1847), a basic principle of physics earlier established independently by James Joule and Julius von Mayer. Helmholtz invented the ophthalmoscope (1851), a valuable diagnostic aid used by doctors in examining the interior of the eye. He also developed a theory of color vision, Color; was an authority on acoustics and hearing; and published works on electrodynamics.
Helmholtz was born in Potsdam and became an army surgeon. After 1847 he taught successively at the universities of Königsberg, Bonn, Heidelberg, and Berlin. In 1887 he became director of a technical institute near Berlin.