340 



TABLES 399-401. 

 RADIOACTIVITY. 



TABLE 399. Stopping Powers of Various Substances for a Rays. 



s, the stopping power of a substance for the a rays is approximately proportional to the square 



root of the atomic weight, w. 



Bragg, Philosophical Magazine, ii, p. 617, 1906. 



TABLE 400. Absorption of /3 Rays by Various Substances. 



the coefficient of absorption for )8 rays is approximately proportional to the density, D. See 



Table 398 for p for Al. 



For the above data the /8 rays from Uranium were used. 

 Crowther, Philosophical Magazine, 12, p. 379, 1906. 



TABLE 401. Absorption of y Rays by Various Substances. 



In determining the above values the rays were first passed through one cm. of lead. 



Russell and Soddy, Philosophical Magazine, 21, p. 130, 1911. 

 SMITHSONIAN TABLES. 



