ABSORPTION OF PHOTO-ELECTRONS 65 



analysis of the behaviour of thin transparent metals of the thick- 

 ness less than lO-'^cm just completed will, it is hoped, furnish 

 the necessary data. 



In a subsec[uent paper it will be shown that a varies very 

 nearly as the cube of the thickness of the metal through which the 

 electron jDasses when the value of a is small. The exact experi- 

 mental relation between a and t is, however, given by the ex- 

 pression a — d(,=mt^, where ^ represents the distance to which 

 a homogeneous beam of electrons can penetrate before its intens- 

 ity is reduced to i- of the original incident value. The data 

 also showed that heavy atoms are not so effective in stopping 

 ail electron as light atoms. 



Department of Physics, 

 The State University. 



