

Absorptior 



and Scattering of 



X-Ray& 





273 



Wave-length 

 (Hull & Eice). 



Wave-length 

 (Siegbalm) 



0*/p) 



Copper. 



Aluminium 



(/Vp) 



Water. 



Wp) 



Paper. 



Wp) 



Paraffin- Wax 



•277xlO~ 8 cm. 

 •276 „ 

 •266 „ 

 •162 „ 

 •257 „ 

 •250 „ 

 •247 „ 

 •240 „ 

 •232 „ 

 •229 „ 

 •225 ., 

 •222 „ 

 '218 „ 

 •212 „ 

 •202 „ 

 192 „ 

 •187 ., 



•i?o „ 



•175 „ 

 '174 „ 

 •166 „ 

 •145 ,. 





3-08 

 3-06 

 2-77 

 2-62 

 2-£8 

 2'33 

 2-27 

 2-10 

 11)4 

 1-86 

 177 

 T71 

 1-66 

 1-54 

 1-40 

 1-29 

 1-20 

 1-10 

 1-03 

 1-02 

 •950 

 •707 



'•391 

 •382 

 371 



■263 



•228 



•210 



•192 

 •153 



•226 

 •229 



•203 







•204 



196 



i 

 i 



•261 



■245 



•252 



•214 



•227 



•186 



•218 

 •210 

 •206 



•203 



•195 

 •192 















































1 





For various reasons the absorbability of X-rays has usually 

 been measured in aluminium. Apart from practical reasons, 

 aluminium was one of the most suitable substances to use 

 because no characteristic radiation from aluminium had been 

 observed within the range of wave-lengths of X-rays in 

 common use. In other words, the wave-length was a simple 

 single- valued function of the absorption in aluminium. Our 

 experiments, however, have shown that aluminium emits a 

 characteristic radiation of wave-length about *37 X 10~ 8 cm.; 

 it is therefore not a suitable substance in which to measure 

 the general absorbability of radiation through a range of 

 wave-lengths such as that used in these experiments. The 

 same objection does not hold in the case of copper, because 

 its K spectral lines are fairly distant on the longer wave-length 

 side and its J spectral lines (assuming they exist) must be 

 somewhere on the shorter wave-length side of the J radiations 

 of the other substances dealt with. 



We have, therefore, plotted absorptions in aluminium, 

 water, filter-paper, and paraffin-wax as ordinates against 

 absorptions in copper as abscissae — thus taking the last-named 

 as the standard of general absorbability. 



The results are given in fig. 1. The scale of ordinates 

 for filter-paper has been made 6/5 times as great as for the 

 ether three. This was necessary as the water and paper 



