1 



THE 

 LONDON, EDINBURGH, and DUBLIN 



'HILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIKNGE. 



[SIXTH SERIES.] 



Y 4 





FEBRUARY 1913. % 



XX 7. Oft aSo??i^ Orfo'Js of an Electron. By 0. G. Dartstk,--' 

 B.A., Lecturer in Mathematical Physics, Victoria University, 

 Manchester* . 



1. TN order to find the characteristics of such processes as 

 JL the absorption by matter of (3 and cathode rays, it is 

 necessary to have a knowledge of the orbits of the electrons 

 as they pass the various charged bodies in matter. According 

 to the theory of Rutherford f, which is strongly supported 

 by experiments J, an atom is composed of electrons and a 

 nucleus of positive electricity of charge such as to neutralize 

 them. The nucleus is seated at the centre of the atom, bears 

 nearly the whole mass, and has its charge concentrated 

 inside a very small region. The present paper is concerned 

 with the orbit of a /3 particle as it passes such a nucleus. 

 On account of its high velocity a /3 particle has apparent 

 mass sensibly greater than that of a slow-moving electron, 

 and during the path the attractive force of the nucleus still 

 further increases it. The variability of mass entirely alters 

 the character of the orbit, with the result that in certain 

 cases it becomes a spiral, going right in to the centre. 

 Numerical calculation shows that these cases should be of 

 fairly frequent occurrence. The physical reason for this 

 may be seen in the following way. On account of the in- 

 creased mass the particle, when near the nucleus, will be 



* Communicated by Prof. E. Rutherford, F.R.S. 



t Rutherford, Phil. Mag. xxi. p. 669 (1911). 



X Geiger, Mane. Lit. & Phil. Soc. Feb. 1911. An account of a much 

 more complete series of experiments by Geiger and Marsden has recently 

 been read at the Vienna Academy. 



Phil Mag. S. 6. Vol. 25. No. 146. Feb. 1913. P 



