(or Roentgen) (1845-1923) German physicist who discovered X-rays 1895. While investigating the passage of electricity through gases, he noticed the fluorescence of a barium platinocyanide screen. This radiation passed through some substances opaque to light, and affected photographic plates. Developments from this discovery revolutionized medical diagnosis. Nobel Prize 1901.
The unit of radiation exposure (X-ray) is named roentgen or röntgen (R) after him.
Röntgen was born in Lennep, Prussia, and studied in Switzerland at the Zürich Polytechnic. He was professor at Giessen 1879–88, then director of the Physical Institute at Würzburg, and ended his career in the equivalent position at Munich 1900–20.
It was at Würzburg Röntgen conducted the experiments that resulted in the discovery of the rays formerly named for him; they are now called X-rays. Today, the unit of radiation exposure is called the roentgen, or röntgen (symbol R). He refused to make any financial gain out of his findings, believing that the products of scientific research should be made freely available to all.
Röntgen worked on such diverse topics as elasticity, heat conduction in crystals, specific heat capacities of gases, and the rotation of plane-polarized light. In 1888 he made an important contribution to electricity when he confirmed that magnetic effects are produced by the motion of electrostatic charges.

Alternative spelling for roentgen, unit of x- and gamma-ray exposure.
Roentgen; unit of dose of ionising radiation, e.g. x-rays or gamma rays.