Joseph von FraunhoferBorn 6 Mar 1787; died 7 Jun 1826 at age 39.German physicist who was the first to study the dark lines in the solar spectrum, which were seen by Wollaston in 1802, but are called Fraunhofer lines. Fraunhofer was not able to explain them, but measured 576 lines. Over 25,000 have now been found in the solar spectrum. These are caused by selective absorption of those wavelengths by atoms of elements, and their relative positions are the same whether the light is produced by heated metals in the laboratory or seen from those gaseous elements in the sun or viewed from other heavenly bodies. Before other scientists so widely adopted the technique, he used a diffraction grating instead of a prism to disperse the spectrum. He also invented a heliometer.« |
