172 



Radiation from Al 

 Thickness of Dome, mm. ... 21 



100 



72 



It has already been shown that the radiation from the 

 sides of the cone is approximately of the same quality as that 

 from a Pb radiator ; we may therefore assume without much 

 possibility of error that the value of A. by Zn for this radia- 

 tion is *34. 



It is now possible to apply the necessary correction to 

 the curve J., fig. iii. A quantity 570(1 -e-(i-5x-34)d^ has been 

 added to the previous readings; the result is shown in the 

 full-line curve B. The last two readings require a slightly 

 less correction on account of the Zn plug cutting off some of 

 the original y radiation which produces the effect from the 

 sides of the cone ; the necessary correction in this case was 

 determined by a separate experiment. 



The quality of the emergence radiation from Zn and 

 from Al was now tested by Zn and by Al domes. The re- 

 sults are given in table i., proper correction being applied in 

 each case for the absorption of the radiation from the side 

 of the cone. 



