340 



Tables 399-401. 

 RADIOACTIVITY. 



TABLE 399.— Stopping Powers ol Various Sa1)Stances for a Rays. 



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



root of the atomic weight, w. 



Bragg, Philosophical Magazine, ii, p. 617, igo6. 



TABLE 400. — Absorption of iS Rays by Various Sabstances. 



a the coefificient of absorption for j3 rays is approximately proportional to the density, D. 



Table 398 for m for Al. 



See 



For the above data the /3 rays from Uranium were used. 

 Crowther, Philosophical Magazine, 12, p. 379, igo6. 



TABLE 401. —Absorption of y Rays by Various Sabstances. 



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. 



