Deflexion of a. Particles through Large Angles. 615 



Table III. 

 Gold. — Variation o£ Scattering with Thickness. 



I. 



11. 



III. 



IY. 



Number of 

 Foils. 



Air equivalent. 

 T in cm. 



Number N of 



scintillations per 



minute. 



Eatio — 

 T 



1 



0-11 



21-9 



200 



2 



0-22 



38-4 



175 



5 



0-51 



84-3 



165 



8 



0-81 



121-5 



150 



9 



0-90 



145 



160 



Similar experiments were carrried out with foils of tin, 

 silver, copper, and aluminium. In each set about 1000 

 scintillations were counted. The results are plotted in fig. 5, 

 where the abscissae represent the thickness of the scattering 

 foil expressed in centimetres of air equivalent and the 

 ordinates the number of scattered particles. Similar cor- 

 rections to the above have been introduced in each case. 



Ear. 5. 



0-8 |- 2 i-e 



Air equivalent of foils. 



2-0 



For all the metals examined the points lie on straight lines 

 which pass through the origin. The experiments therefore 

 prove that for small thicknesses of matter the scattering is 

 proportional to the thickness. If there is any appreciable 



