54 



BIOLOGICAL EFFECTS OF RADIATION 



Interpretation of Absorption Curves.— To bring out the general infor- 

 mation to be inferred from the absorption curves of Figs. 5, 6, and 7, 

 and from this to correlate the curves of Fig. 6 with those of Fig. 5, we shall 

 take a hypothetical absorption curve AB (Fig. 4), in which x gives the 

 thickness of copper filter and 



y = log 



(<) 



U) 



gives the corresponding values of log percentage transmission. Here 

 it will be assumed that the incident radiation h is obtained from an ideal 



1.5 2.0 2.5 



Copper Filter MM. 



YiQ, 6. — Standard copper absorption curves — thick tube. 



X-ray tube of zero wall thickness so that AB is the basic absorption curve 

 corresponding to the given excitation potential. 



As a first case, we wish to show how, from this basic curve, the absorp- 

 tion curve is obtained for the same radiation after it has been modified 

 in quality by traversing a given thickness d of the filter. In this case, 

 h, the intensity emerging from the thickness d, becomes the incident 

 radiation for the new curve. Against new thickness values, 



X' 



X — d 



(^) 



