266 Br Barkia, Phenomena of X-Batj Transmission. 



General Discussion. 



The various phenomena may therefore be connected as shown 

 in the diagram fig. -i. 



Line I represents the absorbability of the secondary radiation 

 characteristic of an element R say. 



Curve II shows approximately the relation between intensity 

 of secondary radiation from R, and absorbability of the primary 

 radiation (measured in Al). 



Curve III shows the relation between ionization in R and 

 absorbability of the primary radiation (measured in Al). 



Curve IV shows the relation between absorption in R and 

 absoi'bability of the primary radiation (measured in Al). 



Curves II and III are based on the assumption that the 

 ionization in air is proportional to the absorption in air for beams 

 differing in penetrating power. The important features are beyond 

 doubt ; the exact shape, however, depends on the accuracy of this 

 assumption. 



There is thus an intimate connection between the absorption 

 of a primary radiation in a substance, the ionization in the 

 absorbing substance (when in the gaseous state), and the intensity 

 of secondary radiation from the absorbing substance. These are 

 periodic functions of the penetrating power of the primary radiation, 

 the three rising and falling together. Though two complete 

 periods have not yet been obtained in any one substance, there is 

 very strong evidence from the behaviour of different substances 

 that there are at least several maxima and minima to be obtained 

 by using a primary radiation of sufficient rauge in penetrating 

 power. The periodicity in intensity of secondary radiation is not 

 one of intensity alone, tor each fresh period brings a characteristic 

 radiation of different penetrating power. 



Sufficient experiments have not yet been made in order to 

 determine if the periodicity is a true jjeriodicity in the behaviour 

 of one system in the atom, or is due to different systems behaving 

 in a similar manner wdieu subject to primary radiations of different 

 penetrating powers. Be that as it may, the experiments on 

 secondary radiation show that there are various characteristic 

 radiations ; the experiments on ionization show that there are 

 various ionizations, only a part of the total ionization being con- 

 nected with one radiation ; the experiments on absorption show 

 that there are various processes of absorption, only a part of the 

 total absorption being connected with one radiation. 



It should perhaps be pointed out that it is owing to the fact 

 that absorption, ionization and secondary radiation connected with 

 one substance are periodic functions of the absorbability of the 

 primary radiation, that these three quantities are also periodic 



