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Anders Jonas Ångström

Anders Jonas Ångström (August 13, 1814 - June 21, 1874) was a physicist in Sweden, one of the founders of the science of spectroscopy. He was appointed keeper of the Uppsala Astronomical Observatory in 1843 and became professor of physics there in 1858. He wrote on heat, magnetism, and, most importantly, optics.

His combination of the spectroscope with photography for the study of the solar system resulted in proving that the sun contains hydrogen. He published his extensive research on the solar spectrum in Recherches sur le spectre solaire (1868), including detailed measurements of more than 1000 spectral lines.

In a paper presented to the Stockholm Academy in 1853, he not only pointed out that the electric spark yields two superimposed spectra, one from the metal of the electrode and the other from the gas in which it passes, but deduced from Leonhard Euler's theory of resonance that an incandescent gas emits luminous rays of the same refractive capacity as those which it can absorb. This statement, as Sir Edward Sabine remarked when awarding him the Rumford medal of the Royal Society in 1872, contains a fundamental principle of spectrum analysis, and though for a number of years it was overlooked it entitles him to rank as one of the founders of spectroscopy.

He was the first, in 1867, to examine the spectrum of the aurora borealis, and detected and measured the characteristic bright line in its yellow green region.

The angstrom units with which the wavelength of light is measured are named for him. The units are used in crystallography as well as spectroscopy.

His son, Knut Johan Ångström (1857-1910) was known for his research at Uppsala University on solar radiation, the radiation of heat from the sun and its absorption by the earth's atmosphere. For his research, he devised various delicate methods and instruments, including his electric compensation pyrheliometer, invented in 1893, and apparatus for obtaining a photographic representation of the infrared spectrum in 1895.

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