. Technical paper. y Meyer and Hess far rating mesothorium : a. Ioniza-tion chamber ; b, lead ; c, zinc sheet; d, zinc disk ; e, Wulf electrometer. formula. For the experimental arrangement of Meyer and Hess,the following simplified formula of King applies: _ f(uT)1 1-cosO where It is the current produced after passage through a thicknesst of the screen, and 0 is the angle diown in figure 4. I e~j-fc %J 00 46 MESO THORIUM. APPLICATION OF KIXc/s FORMULA. To test the applicability of Kings formula. Meyer and Hessmeasured the absorption of the gamma rays from the followingsources, in the apparatu
. Technical paper. y Meyer and Hess far rating mesothorium : a. Ioniza-tion chamber ; b, lead ; c, zinc sheet; d, zinc disk ; e, Wulf electrometer. formula. For the experimental arrangement of Meyer and Hess,the following simplified formula of King applies: _ f(uT)1 1-cosO where It is the current produced after passage through a thicknesst of the screen, and 0 is the angle diown in figure 4. I e~j-fc %J 00 46 MESO THORIUM. APPLICATION OF KIXc/s FORMULA. To test the applicability of Kings formula. Meyer and Hessmeasured the absorption of the gamma rays from the followingsources, in the apparatus figured, using screens of zinc and lead:(1) Radium (RaC) : (2) pure radiothorium (ThD) ; (3) meso-thorium free from radium and radiothorium (MsTh 2). The meas-urements gave values showing that agreement with the formula ofKing was not obtained when the usual values of Soddy and Russell(see Table 1, p. 7) for the absorption coefficients were used. Asatisfactory agreement however appeared when the following absorp-. Figcee 4.—Ionization chamber of the Meyer-Hess apparatus: a, Screen ; b, ionization chamber. tion coefficients for lead were introduced, all of which were mate-rially higher than the older values in parenthesis: ThD. ji— () : RaC, [ () : MsTh 2, [ () The higher values were used by Meyer and Hess in their calcula-tions. The calculated values for the ionization current were reducedto the scale where 1=, when no screen intervenes, for each sub- stance. The ratio of the values for ThD and MsTh 2—that isiwyriTogave the values of the factor K to be used in the equation for thecurrent It=X1M-T-KX2R, for different thicknesses of lead. In otherwords the factor K expressed the gamma radiation from ThD interms of MsTh 2. To express the combined gamma radiation from MsTh 2MsTh 2 and ThD in terms of radium, the ratio ^ p was introduced. This ratio is designated by K. That is, the productsKIt gave the value of the ionization current of spec
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