Wilhelm Roentgen. Portrait of German physicist Wilhelm Konrad Roentgen (1845-1923), made shortly after his discovery of X-rays in 1895. Roentgen was professor of physics at Wurzburg. While using an electric discharge tube in a darkened room he noticed that a card coated with barium platinocyanide glowed when the tube was switched on. The radiation causing this effect was not blocked by an intervening wall or even by a thin sheet of metal. Roentgen called the new rays X- rays and suggested they were a form of electromagnetic radiation akin to light but of shorter wavelength. The discovery won him the first Nobel Prize for physics, in 1901.