Thin Films of Elements exposed to Bontyen Rays. 137 



three results, which are obviously in error, it will be seen 

 that there is a rough agreement with this law for the minor 

 groups. 



Table II. 





Incidence 



of Silver (K) X-rays. 



; 

 Incidence c 



)f Barium (K) X-rays. 



1 



Element 



Kinetic 



Range (d) 





Kinetic 



Range (d) 





(S). 



energy (E) 



in air 



E dK 



energy (E) 



m air 



E/rf* 





of sub- 



at C & 



of sub- 



at 0° & 







group 



760 mm. 





group 



760 mm. 







+ n Q h. 



from fig. 8. 



-7-» A. 



-r »„*■ 



from fig. 9. 



-r» A. 







cm. 







cm. 





As 



741 



•228 



1 550 



1491 



•59.") 



1930 



Se 



68 L 



•193 



1550 



1431 



•455 



2120 



: Zr 



304 



•157 



*770? 



1054 



•438 



1590 



Ag 









494 . 



•140 



1320 



; Sn 









215 



•128 



*600? 



i Sb 









122 



• 1)70 



*460? 



: £a 



1245 



•333 



21H0 









Au 



760 



•175 



1820 



1510 



•595 



1960 



Pb 



683 



•164 



1690 



1433 



■560 



1920 



>Bi 



656 



•164 



1620 



1406 



•427 



2150 

 2368 



As 



1618 



•60 t 



2090 : 



2368 



10 t 



* These numbers are got from the small ranges Avhere the error must be 

 ■considerable. 



t Obtained from figs. 5 and 6 (PI. III.). These are the maximum ranges 

 for the incidence of Ag and Ba X-rays respectively. 



Some further considerations on the potential energy 

 of the electrons. 



There seem to be two distinct points of view : (1) If an 

 electron be removed from a " K " ring an " L >} electron 

 falls into its place, an '* M " electron into the place of the 

 " L " electron, and so forth. During this process the one 

 atom would yield a series of line spectra. This is the view 

 adopted up to the present, and also that all the atoms of a 

 given substance exposed to X-rays of a given type are not 

 necessarily depleted originally of K electrons — a neighbouring 

 atom may be depleted of an L electron or an M electron. 

 (2) If an electron be removed from a K ring, this ring- 

 readjusts itself from one stable state to the next, during 

 which there is an emission of K radiation. It seems to me 

 that according to (1) the potential energy of the K electron 

 should be (hv K + hv L + etc.), and according to {%), only >Jiv K ). 



