ABSTRACT
This chapter explores that when the X-ray spectrometer is fitted with an analyser consisting of a reflecting crystal, which becomes to X-rays a diffraction grating, a spectrum of the radiation is produced which resembles the ordinary spectrum. The characteristic radiations appear as K and L series lines, but each series is made up of a strong line and a weaker one a little distance from it. The penetrating character of the radiations increases the atomic weight of the element emitting them, and by using the aluminium as an absorbing medium the penetrability can be plotted against atomic weight, giving two similar curves one for the K-radiations and one for the L-radiations. The K series for elements of higher atomic weight than silver is difficult to excite, because the velocity of cathode rays necessary to excite a given radiation increases with the frequency of the radiation.
