Properties of Thin Films of Platinum. 



119 



different metals *. It was shown that the greatest emission 

 is normal to the electrode, and as the angle increases the 

 emission diminishes. This point need not be considered 

 further with regard to the velocity measurements, as it 

 seems unlikely that reflected electrons can alter the 

 maximum potential attained by the radiated films *j\ 



E 



5. Measurements of the Ratios ^ . 



The results for one series of experiments to find how 

 "F 1 IT 



the ratios -^ currents and -^ velocities vary with the 

 I I J 



thickness of the film are shown in Table I. The relative 



Table I. 



Thickness 

 of Film. 



E 



-r currents. 



■p 



- yelocities 



1 



(in volts). 



40 seconds 



1-311 

 1-281 

 1154 

 1063 



0-787 



1-071 

 1-041 

 1022 

 1033 

 0-977 



80 „ 



120 „ 



200 „ ... 



360 „ 





Fio-. 2 



1-2 



k 



i-o 



0-9 



0-8 



0-7 



























t s s ^ 



fes. 



















> 



c^ 



j< 















*s 



<-Ocr 





€ 



) >s. 

















f £S 











































































so 



160 £4-0 



Th/ckhess of F/lm 



320 



400 seconds 



thicknesses of the films are given in terms of the time of 

 deposit. The results of this table are shown graphically in 



E E 



fig. 2, where the ratios y currents and y velocities are 



* Ann. der Phys. Bd. xxxi. p. 791 (1910). 



f Ladenburg, Phys. Zeit. viii. p. 590 (1907) ; Hughes, loc. cit. 



