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
Wilhelm Dürr the Younger assistant professor at the Munich Academy of Fine Arts and, in 1892, professor. There he taught mainly life classes. At the end of his life, he was seriously ill and only painted a few pictures. In Dachau, Wilhelm-Dürr-Straße is named in honour of the painter. Wilhelm Dürr the Younger Wilhelm Dürr the Younger (24 August 1857, Freiburg im Breisgau, Baden – 23 February 1900, Munich) was a German painter and draughtsman, as well as a professor at the Academy of Fine Arts in Munich. Dürr was the son of the painter Wilhelm Dürr the Elder (1815–1890) and his wife Berta