SCATTERING COEFFICIENTS 



21 



elements must be taken into consideration. Representative values are 

 given in Table 1-5 for some of the more common therapeutic filters. 



60 70 80 90 100 



Kilovolts across x-ray tube 



110 



120 



Fig. 1-9. The per cent transmission of aluminum niters at increased kilovoltage 

 using a constant source of potential. The tube wall was 1.3 mm cerium glass. (After 

 L. S. Taylor, Natl. Bur. Standards.) 



TABLE 1-5 



By courtesy of C. W. Hewlett [1921]. 



For all practical purposes the various influences contributing to the 

 scattering of the energy for any given metal are separable into: 



1. The influence of thickness on scattering. 



2. The influence of density of the filter on scattering. 



3. The wavelength of the incident energy. 



4. The departure of the incident beam from a parallel column. 



The scattering of x-radiation in passing through matter is dependent 

 on the thickness of the filter in such a way that each succeeding centi- 

 meter of filter thickness converts the same fractional amount of the inci- 



