﻿Absorption of Homogeneous ft Rays. 



121 



when various thicknesses of foil were placed over E. The 

 current was then reversed so that no ft rays passed through 

 C, and similar readings were taken. A curve of the type 

 AA (fig. 2) was obtained when the field was direct, and one 

 of type BB when the field was reversed; the two curves 



Fig. 2. 



100 



•3 -5 -7 



THICKNESS IN GMS. 



coincided for a very thick absorbing screen. The curve AA 

 represents the combined ft and y ray effect in E, the curve 

 BB represents the 7-ray effect alone, so that the curve CC, 

 which is obtained by subtracting curve BB from the curve 

 AA, represents the curve of ft ray absorption. The inter- 

 pretation of the curve BB will be discussed later. 



After a small thickness of matter had been traversed, an 

 approximately linear relation (see curve CC) was found to 

 exist between the ionization and the thickness o\' the ab- 

 sorbing screen. The curves CC for various velocities are 

 shown in figs. 3 and 4. 



