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
Anton Wilhelm Plaz Anton Wilhelm Plaz Anton Wilhelm Plaz (1 January 1708, Leipzig – 26 February 1784, Leipzig) was a German physician and botanist. From 1723 he studied medicine at the universities of Leipzig and Halle, receiving his doctorate at the latter institution in 1728. In 1733 he became an associate professor of botany at Leipzig, where afterwards, he successively served as a full professor of botany (1749–54), physiology (1754–58), anatomy and surgery (1758), pathology (1758–73) and therapy (1773–84). From 1773 to 1784 he was dean to the medical faculty at the university. He was a member of the Römisch Kaiserlichen Akademie der