Joseph von Fraunhofer

Born Mar. 6, 1787, in Straubing; died June 7, 1826, in Munich. German physicist.

The son of a glazier, Fraunhofer first worked in his father’s workshop. After his father’s death in 1798, he studied and then worked for a mirror-maker and glass cutter in Munich. In 1806 he became a journeyman at a mathematics and optics institute (located in Munich, then in Benediktbeuern), where lenses and optical devices were made. In 1809 he became one of its managers, and in 1818, its general manager. In 1823, Fraunhofer was appointed conservator of the physics cabinet of the University of Munich. That same year he became a member of the Bavarian Academy of Sciences, and in 1824, a member of the Leopoldine Academy.

Fraunhofer improved the techniques for manufacturing large achromatic objectives and invented the eyepiece micrometer and heliometer. In 1814, while studying the refractive indexes of different types of glass, he discovered, independently of the British physicist W. H. Wollaston, and described absorption lines in the solar spectrum (Fraunhofer lines). In 1821 he used a diffraction grating to study spectra, the first one to do so. Fraunhofer also proposed a method of observing the diffraction of light in parallel rays.