Nikola Tesla film in his laboratory in previous experiments (later identified as ""Roentgen rays"" or "X-Rays"). His early experiments were with Crookes tubes, a cold cathode electrical discharge tube. Tesla may have inadvertently captured an X-ray image—predating, by a few weeks, Wilhelm Röntgen's December 1895 announcement of the discovery of X-rays when he tried to photograph Mark Twain illuminated by a Geissler tube, an earlier type of gas discharge tube. The only thing captured in the image was the metal locking screw on the camera lens. In March 1896, after hearing of Wilhelm Röntgen's discovery of X-ray and X-ray imaging (radiography), Tesla
Roentgen (unit) In radiation protection the absorbed dose is the energy absorption which is an indication of likely acute tissue effects occurring at high dose rates, and from low levels of absorbed dose the equivalent dose, representing the stochastic health risk, can be calculated; for which the current SI units used are the gray (Gy) and the sievert (Sv) respectively. The roengten has been redefined over the years. It was last defined by the US National Institute of Standards and Technology (NIST) in 1998 as , with a recommendation that the definition be given in every document where the roentgen is used.