338 MA<;M:TI-M 



of radius d in which the electron round < 



from the N.S.P. If it^ velocity i- V it will IIM 



force II, v inuanU ;m<l M) it- 'fmji: !1 1>< in 



NtoNj. The total force l< the ccnl're it' tl 



47r 2 N 2 wd + lift* = 47r 2 NW 4- J^rNJIrr/, putting 2-N^/ 1, 



The acceleration is (4-Tr 2 N 2 + 2- m<l the l'm|ucn. 



given by 



N . 



and as the second term on the right \ith 



the first, in it we m.iy put N tor N,. ^> t ; 



\ \ 



A oounier-clodcwiM motion v^ill 1. : D ut- 



\\aid-, and M> the frccjiu-ncy i^ reduced. I \ n 1>\ 



V N 



or approximately 



There are therefore ^ t the original 1 y N 



stil ^remaining in the vihrations nlnn^ the lines of force, nnl them 

 are two sets of circular motions in a plane perpcndiculni 

 lines of i <1 \\ith fivijucneies, one rather greater and tin- 



other rather less than \ 



Consider the li:lit _u r in.i: out c.juatoi ;lar vibra- 



tions will only send linear vil. in that M, for it is in 



their own plane, and the direction of vil> n the waves will 



be perpendicular to the lin 



source aloni: the lines of force will send out vibrations parallel to 

 that direction and of t li- 



the light in a spectroscope, ue mav expect to lia\. a line in tin- 

 position of the original line polarised in the equatorial plane, or, 

 as it is easier to picture, vi! ..arallrl to the lines of force, 



and this should he Hanked 1>\ Uo lines \\ith \il>i erse 



to the lines of force. If we consider the light travelling out axially, 

 then the vibration along the lines of force \\ith the orii: 

 frequency sends n<> waves in that direction, but the Uo opposite 

 sets of circular vihrations send opp ilarly polarised rays, 



and in a spectroscope we ought to have two lines, one on each side 

 of the original position, and the light in them should be circularly 

 polarised in opposite din 



Zeeman's verification. Zeeman found that experiment 

 verified these anticipations of theory. But further research with 



