On 8 November 1895, Wilhelm Conrad Roentgen accidentally discovered an image cast from his cathode ray generator, projected far beyond the possible range of the cathode rays. Further investigations showed that the rays were generated at the point of contact of the cathode ray beam inside the vacuum tube, that they were not deflected by magnetic fields, and they penetrated many kinds of matter.
A week after his discovery, Roentgen took an X-ray photograph of his wife’s hand which clearly revealed her wedding ring and the bones. The photograph electrified the general public, and aroused great scientific interest in the new form of radiation. Roentgen named the new form of radiation X-radiation (X standing for unknown). Hence the term X-rays. The image produced by X-rays are due to the different absorption rates of different tissues. Calcium in bones absorbs X-rays the most, so bones look white on a film recording of the X-ray image, called a radiograph. Fat and other soft tissues absorb less, and look gray. Air absorbs the least, so lungs look black on a radiograph. Roentgen won the Nobel Prize for Physics in 1901 for his discovery of X-rays.
