Scattering of X-rays and Atomic Structure. 



227 



length) the " K " radiation appeared. At this stage this 

 had a penetrating power differing little from that of the 

 primary and thus from that of the scattered radiation, so it 

 became impossible to separate them by the absorption method. 

 Consequently no values were obtained of the scattering from 

 silver of radiation of wave-length near to that of the 

 characteristic radiation. 



When, however, radiation of very much shorter wave- 

 length was used, the fluorescent radiation of series K was 

 still excited, but this was removed by transmission through 

 a sheet of aluminium, leaving only the very penetrating 

 scattered radiation to be compared with that from aluminium. 

 As an example of the results showing the similarity of the 

 two penetrating radiations scattered from silver and from 

 aluminium, the ratios of the ionizations produced by these 

 in the two electroscopes, after transmission through various 

 thicknesses of aluminium, are given below. 



Thickness in Al 

 traversed. 



Ratio of Ionizations produced by 



the scattered radiations from Ag 



and Al in arbitrary units. 



2-2 cm. 

 16 „ 

 2-8 ,.. 

 1-6 „ 



•223 

 •222 

 •219 

 •219 



The constancy of the numbers in column 2 shows that the 

 two radiations were transmitted through aluminium to 

 exactly the same extent. 



Tin and Lead. — The methods applied to copper and silver 

 were used in examining the scattering from lead and tin 

 respectively, the Cu " K " radiation being not unlike the Pb 

 "L ,J radiation, and Ag and Sn " K " radiations being of 

 neighbouring wave-length. 



Considering the lack of perfect homogeneity of the beams 

 employed, the agreement between the results obtained by 

 the two methods was quite close. All the general features 

 which are indicated below were shown by both methods ; 

 consequently it was unnecessary to take anything like a 

 complete series of observations by both these methods. The 

 second method (b) was subsequently adopted, so that the 

 results given in Table II. are strictly comparable, and any 

 irregularities occurring are not such as might be expected 



R2 



