the Absorption of JRontgen Rays. 



745 



If A is the area of the primary beam, the energy of the 

 secondary radiation emitted by a thin layer of thickness dx 

 in unit time = kIAdx, 



where k is a constant depending on the character of the 

 incident radiation and on the material of the plate. It 

 will be called the transformation coefficient *. 



(O 



But of this the fraction -: — e 



47T 



\.p-x) en ters the electroscope, 



where co is the average solid angle subtended by the 

 aperture into the measuring electroscope at points in 

 this layer, and X 2 is the coefficient of absorption of the 

 secondary radiation in the substance of the plate itself, 

 when the effect of obliquity of the secondary rays and the 

 absorption in air and the thin window may be neglected. 



Fig-. 2. 



The total energy of secondary radiation entering the electro- 

 scope per second 



c 



477 



^ 



CO 



47T 



Jo 



_cok AI v V) 



Energy of Secondary Radiation entering electroscope 

 Energy of Primary Radiation entering electroscope 



wL \ AI , _ v 



47T \. 2 — \i 



■<v 



AV 



-XJ 



* This coefficient is so called by analogy with the absorption coefficient* 

 dF 



•-— = — 7cl, where —dE is the energy emitted by a thin layer of unit area 

 dx °* J 



and thickness dx in unit time. 



