Secrion III., 1911. [97] Trans. R. S. C. 
Absorption Problems in Radioactivity. 
By Louis V. Kine, B.A. (Cantab.), Lecturer in Physics, McGill 
University. 
(Presented by Prof. A. S. Eve.) 
Read May 17th, 1911. 
1. The intensity of B- and y- rays in their passage through 
matter decreases approximately according to the exponential law 
I, being the intensity at an arbitrary origin x — 0 as measured by the 
ionizing power of the rays, and « the co-efficient of absorption. Under 
these conditions it can easily be shown that the intensity at a distance 
r from a point-source of rays in a medium whose co-efficient of NU 
tion is kK is given by 
Fie. 1. 
If then we have a mass of radioactive matter enclosed by a surface 
S, the intensity of the primary radiations which reach P can be easily 
