Roentgen (unit) Roentgen (unit) The roentgen or röntgen () (symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays. It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air. In 1928 it was the first international measurement quantity for ionising radiation to be defined for radiation protection, and was an easily replicated method of measuring air ionization directly by using an ion chamber. It is named after the German physicist Wilhelm Röntgen, who discovered X-rays. Although relatively easy to measure, it had
Friedrich Wilhelm Theile Friedrich Wilhelm Theile Friedrich Wilhelm Theile (11 November 1801, in Buttstädt – 20 October 1879, in Weimar) was a German physician and anatomist. In 1825 he received his medical doctorate from the University of Jena with the dissertation-thesis "De Musculis nervisque laryngeis". From 1828, with Heinrich Wilhelm Ferdinand Wackenroder, he was in charge of the pharmaceutical institute at Jena. In 1831 he became an associate professor, and three years later relocated to the University of Bern as a full professor of anatomy. From 1853 he practiced medicine in Weimar, during which time, he largely concerned himself with literary activities. In