A Determination of the Wave-Length of theKαLine of Carbon

A simplified type of vacuum spectrometer utilizing a plane glass grating with 250 lines per mm was used to measure the wave-length of the $K\alpha$ line of carbon. A water-cooled metal x-ray tube with tungsten cathode was connected directly with the spectrometer without the interposition of any absorbing screen in the x-ray beam. The measurements were made under varying conditions. The angle of incidence being varied from 20′ to 50′ and the distance from grating to plate from 50 cm to 80 cm. A weighted mean of all determinations gives the wave-length of the $K\alpha$ line of carbon as 45.4A.