. Radioactive transformations . Sho rt Expos ure. i? 40 / (0 E / 1 ^ J 15 60 75 Time in Minutes. Fig. 26. Variation of the activity, measured by the $ rays, of a body exposed fora short interval to the radium emanation. entering the electroscope. This insures that the /3 as well asthe a rays are cut off completely. The identity of the /3 and 7 ray curves shows that the twokinds of rays always occur in the same proportion. This rela-tion is a strong argument in favor of the view that the 7 raysare a type of X-rays, which are set up at the moment of the ex-pulsion of the /3 particle from radioac
. Radioactive transformations . Sho rt Expos ure. i? 40 / (0 E / 1 ^ J 15 60 75 Time in Minutes. Fig. 26. Variation of the activity, measured by the $ rays, of a body exposed fora short interval to the radium emanation. entering the electroscope. This insures that the /3 as well asthe a rays are cut off completely. The identity of the /3 and 7 ray curves shows that the twokinds of rays always occur in the same proportion. This rela-tion is a strong argument in favor of the view that the 7 raysare a type of X-rays, which are set up at the moment of the ex-pulsion of the /3 particle from radioactive matter. This ratiobetween the intensities of the two kinds of rays has been shownto hold in every case so far examined, and suggests that the 104 EADIOACTIVE TRANSFORMATIONS 7 rays bear the same relation to the yS rays that the X-rays bearto the cathode rays. Theory of Successive Changes in Radium We shall show later that the peculiarities of the decay curvesof the active deposit of radium for any time of exposure, whether. 40 60 80 100 120 Time in Minutes. Fig. 27. Variation of the activity, measured by the £ or y rays, of a body exposedfor a long interval to the radium emanation. the activity is measured by the a, /3, or 7 rays, can be satisfac-torily explained on the following assumptions: — (1) That the emanation is transformed into a product calledradium A, which emits only a rays, and has a period of 3minutes. (2) That radium A is transformed into radium B, which hasa period of 28 minutes, and is transformed without the emis-sion of a, /3, or 7 rays. In other words, radium B is a raylessproduct. TRANSFORMATION OF RADIUM 105 (3) Radium B is transformed into radium C, which has aperiod of 21 minutes, and emits during its transformation a, /3,and 7 rays. ^ We thus have to deal with the problem of three successivechanges. Since, however, the first product, radium A, israpidly transformed with a 3 minute period, the amount of itremaining, for example, 21 minutes after
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