Showing posts with label roentgen. Show all posts
Showing posts with label roentgen. Show all posts

Units of Radioactivity

        Physical Quantity                               SI Unit                                 Non-SI Unit
             Activity                                       Becquerel                                Curie (Ci)

        Absorbed Dose                                 Gray                                        RAD

        Dose Equivalent                                Sievert                                     REM

        Exposure                                         Coulomb/Kg                              Roentgen

Discovery of X-rays

Wilhelm Roentgen was professor of physics at university of Wurzburg, Germany when he discovered X-rays in 1985. The discovery was entirely serendipitous; Roentgen was merely studying a beam of electrons in a highly evacuated glass vessel. When the electrons, moving at great speed slammed into glass wall, they produced a very high penetrating radiation - a wholly unexpected occurrence. Roentgen first noticed the radiation when it caused a paper coated with Barium Platino-cyanide to glow. The chemical compound was a standard detector of UV light which causes the chemical to fluorescence i.e. to emit visible light after it has absorbed UV light. But Roentgen's evacuated vessel was tightly covered with black cardboard and so no UV light could emerge from it. The glow must be some other kind of radiation.

When he announced the discovery of the new radiation, Roentgen wrote:

"I posesss, for instance, photographs of ............the shadow of bones of hand, the shadow of a covered wire enclosed in a box.........."

Earlier in the paper, he noted that "the darker shadow of bones is seen with in the slightly dark shadow image of hand itself.

The new radiation quickly became a diagnostic tool in hospitals all over the world. Roentgen could not determine what the rays are made of and thus rays are named as X-rays.