= Joseph von Fraunhofer
{c}
{tag=Physicist}
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<Joseph von Fraunhofer> combined precision manufacture of optical glass with quantitative <spectroscopy>. He systematically mapped dark lines in the solar <spectrum> and used them as reproducible reference points for comparing <refraction> in different glasses. His <diffraction gratings> supplied another way to separate and measure <wavelengths>. The <Fraunhofer lines> thus served an immediate engineering purpose before their later interpretation as signatures of absorbing matter: they let optical experiments return to the same identifiable spectral features.<Joseph von Fraunhofer, Fraunhofer Society biography>[His Achievements: optical glass, gratings, dark solar lines and refraction standards]{ref}
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{title=Portrait of <Joseph von Fraunhofer>}
{description=Unknown artist; Berlin-Brandenburg Academy archive source. Public domain (PD-old as declared on Commons). Source and usage information on the linked Wikimedia file page.}
{source=https://commons.wikimedia.org/wiki/File:Joseph_von_Fraunhofer_Portrait.jpg}
{width=250}
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