X-Ray History from LIXI, Inc.

Wilhelm Röntgen

In October of 1895, Wilhelm Conrad Röntgen (1845-1923) who was professor of physics and the director of the Physical Institute of the University of Wurburg, became interested in the work of Hillorf, Crookes, Hertz, and Lenard. The previous June, he had obtained a Lenard tube from Muller and had already repeated some of the original experiments that Lenard had created. He had observed the effects Lenard had as he produced cathode rays in free air. He became so fascinated that he decided to forego his other studies and concentrate solely on the production of cathode rays. One Friday evening, on November 8, 1895, he worked alone in his laboratory. It was the beginning of the weekend and all of his assistants had gone home. He had set up his experiment using a Crookes tube fitted with an anode and cathode, separated from each other by a few centimeters in the tube. He used a Rhumkoff induction coil to produce a difference of potential of a few thousand volts, knowing that a stream of charged particles would originate in the cathode and would be attracted to the anode.

The laboratory Röntgen worked in that evening was very similar to all other laboratories of those who worked before him, but the conditions that existed that evening varied in three very important ways. His laboratory was dark, his tube was covered with a light-proof cardboard jacket and a screen of fluorescent material laid on a table a few feet away from the apparatus. While passing the discharge, he suddenly noticed a shimmering light on the table top. He could not believe his eyes, so he again repeated the experiment. He released the discharge many times producing the same results each time. Greatly excited, he realized that the green fluorescence was emanating from the screen. He repeated the experiment again, this time moving the screen further and further away and he still received the same results.

Röntgen knew the fluorescence could not be produced by the cathode rays since it was well known that they could not penetrate through the wall of the tube. Visible light could not be the stimulus since the tube was covered with a shield which was opaque to light. He boldly hypothesized that he must have been producing some unknown type of radiation.

Röntgen spent the next eight weeks in his laboratory repeating his experiments. He ate and even slept in his laboratory as he attempted to determine if the rays could penetrate substances besides the air. He placed various objects between the tube and screen and he found that the screen still fluoresced but with different intensities depending on the material being used. When he placed a lead disk, which he was holding, in the cathode ray path he was astonished to find the shadow of the round circle appeared on the screen along with the outline of his thumb and forefinger and within them the bones of his hand! He replaced the screen with a photographic plate and employed his wife Bertha (Frau Röntgen) to place her hand on the photographic plate while he directed the rays at it for fifteen minutes.

Röntgen hurriedly prepared his notes so that his first report "On a New Kind of Rays" could be published in the Proceedings of the Physical Medical Society of Wurburg on December 28, 1895. Not knowing what these emanations were he uses the term x-ray to describe the rays he was producing. Later, in 1896, he accepted the Rumford gold medal of the Royal Society and in 1901 he would be the first to receive the Nobel Prize for physics, but he bequeathed the Nobel prize money to scientific research at Wurzburg.

The first x-ray
Frau Röntgen's left hand