Roentgen (unit) Roentgen (unit) The roentgen or röntgen () (symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays. It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air. In 1928 it was the first international measurement quantity for ionising radiation to be defined for radiation protection, and was an easily replicated method of measuring air ionization directly by using an ion chamber. It is named after the German physicist Wilhelm Röntgen, who discovered X-rays. Although relatively easy to measure, it had
The Amazing Race en Discovery Channel 2 route markers in this season were coloured blue and black, including the clue envelopes and the Pit Stop. None of the eliminated teams were present at the Finish Line. Applications were accepted from 13 December 2009 and finished on 8 February 2010. Semi-finalist interviews were held sometime in March 2010 and the final casting interviews took place around April 2010. According to Discovery's official website, the four official sponsors of the second season of "The Amazing Race en Discovery Channel" were Bridgestone, Samsung, Visa and Wii Party. The sponsors played a major role in the series by providing prizes and