FRAUNHOFER, JOSEPH VON German optician and physicist, was born at Straubing in Bavaria on March 6, 1787, the son of a glazier who died in 1798. He gained experi ence in working optical glass and obtained work at the Utz schneider optical institute at Benedictbeuern, near Munich, of which he in 1818 became sole manager; the institute was in 1819 removed to Munich. Fraunhofer acquired great skill in the manu facture of achromatic lenses and various optical instruments. While measuring the refractive index of glass of various kinds he noticed and made use of the D lines in the sodium spectrum. Con tinuing this work he observed the dark lines in the solar spectrum. His researches were published in the Denkschri f ten der Mum chener Akademie for 1814-15. These dark lines had been noted earlier by W. H. Wollaston (Phil. Trans., 1802), but were for the first time carefully observed by Fraunhofer, and have on that account been designated "Fraunhofer's lines." He mapped 576 of these lines, the principle of which he denoted by the letters of the alphabet from A to G; and by ascertaining their refractive indices he determined that their relative positions are constant, whether in spectra produced by the direct rays of the sun, or by the reflected light of the moon and planets. The spectra of the stars he obtained by using, outside the object-glass of his tele scope, a large prism through which the light passed to be brought to a focus in front of the eye-piece.
In 1823 he was appointed conservator of the physical cabinet at Munich, where he died on June 7, 1826.
See J. von Utzschneider, Kurzer Umriss der Lebensgeschichte des Herrn Dr. J. von Fraunhofer (Munich, 1826) ; G. Merz, Das Leben and Wirken Fraunhofers (Landshut, 1865).