Röntgen (or Roentgen), Wilhelm Konrad (1845–1923)

German physicist. He was awarded the Nobel Prize for Physics in 1901 for his discovery of X-rays in 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.

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 that Röntgen conducted the experiments that resulted in the discovery of X-rays (originally named after him). 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.