Optical Isomerism, and tlw Ring- Electron. 421) 



is exactly the same as for an electron of the classical type 

 moving in an orbit equal in size to the ring with a speed 

 equal to that of the electricity of the ring. These results 

 simplify very greatly the consideration of problems con- 

 nected with the ring-electron. 



In the case of an ordinary electron exposed to light, the 

 incident vibrations of the light bring about forced vibrations 

 throuoh the action of the electric vector in the wave-front. 

 With the modification here proposed, the effects are more 

 complicated, for the ring-electron will be acted upon both 

 by the electric and magnetic vectors. Any rotation of the 

 plane of the ring, which may be produced by the magnetic 

 force of the light-wave, will be neglected. There is a more 

 important effect due to the alternating electromotive force 

 acting round the ring and producing changes in the magnetic 

 moment of the equivalent magnet. Consider a fixed ring- 

 electron, the axis of the ring being parallel to the axis of x. 

 When this is exposed to a light-wave, there will be an electro- 

 motive force * in the ring given by 



i (oY dZ\ 

 = -Ac =— — _ , approximately, 

 \OZ 0[/J 



where A is the area of the ring. If this alternating E.M.F. 

 be represented by E cospr, there will be round the ring an 



IT 



induced current differing in phase by 9 from the electro- 



. . P , t i E sin pt ml 

 motive force, and represented by - — '—. Uie magnetic 



moment of the electron will be increased by an amount 



j 1 , and in consequence there will be a mechanical 



force acting upon the electron proportional to this increase 

 and to the space variation of the controlling magnetic field. 

 Thus the equation of motion of the electron will contain a 



term of the form eft =r ~ <- ) required by Drude's theory, 

 •' \o~ Ol/J H 



the coefficient ef being proportional to A 2 /L, and depending 

 also on the character of the magnetic field due to the re- 

 mainder of the molecule or to any external magnetic system. 

 It then follows, as shown by Drude, that there will be two 



* Following Drude, E, a, /3, y are in electromagnetic units, whilst 

 e, X, Y, Z are in electrostatic units. 



