Primary and Secondary y Rays. 935 



Relation between coefficients of absolution of the secondary 

 y radiation. 



The area of each radiator is (11*1 x 11*1) cm. 



Radiator. 



Direct radiation. 



Electroscope at 

 angle 25°. 



Electroscope at 

 angle 55°. 



5 era. carbon . 



The coefficient of 



absorption is 



= •63 



The coefficient of 



absorption is 



= 1-20 



The coefficient of 



absorption is 



= 1-77 



10 cm. carbon . 



= 65 



=118 



= 1-70 



22 cm. iron . . . 



= •65 



=1*17 



= 1-68 



5 era. iron ... 



= •59 



=105 



= 155 



•416 era. lead . 



= •625 



=1-11 



= 1-65 



Effect of area oft 



'adiator. 



Radiator. 



Area. 



Electroscope at angle 80°. 



2*2 cm. of iron ... 

 2'2 era. of iron ... 



(HI X U'l) cm. 



(22x22) cm. 



X = l-82 

 X = l-96 



through 2 cm. of iron is the same as that passing through 

 10 cm. of carbon. For any position of the electroscope this 

 equality of ratio seems to hold true. This points to the con- 

 clusion that the secondary radiation is the primary radiation 

 scattered. If the radiation was a true secondary radiation 

 it would be expected that the quality would depend on the 

 material. 



In the second table it is shown that an increase in area of 

 the radiator causes the secondary radiation to become softer. 

 This is no doubt due to the fact that as the area increases, 

 a more oblique secondary radiation will come from the 

 radiator. 



Effect of Screens round Radium. 



Experiments were made to examine the effect of different 

 screens round the radium. The electroscope was 3 mm. 

 thick, and 8*75 mm. of lead was used as an absorbing screen. 



Radiator. 



Thickness. 



Radium unscreened. 



Screened. 





10 cm. 

 2'5 era. 



A = 2-68 

 X = 160 



X=237 

 X = l-40 







