Effect on Thin Films of Platinum. 425 



absorbed by the film as obtained from the curve A (fig. 2) 

 and curve A (fig. 3) are given for various thicknesses, as- 

 also are the photo currents for unit absorption of light. 



Fig. 3. 



60 





40 







a 2C 



< 

 ,*0 







A 







1 



i 







\ 



\ 





1 



! 



A 



• 





( 





\ 



/ 



, 





/ 







; 







y/X 







^B 















150 



00 



50 



:§ 



a, '^ 



E ^ 







c3 



10-0 '2 00 3 00 



Tune of Deposit of Film in Seconds. 



Curve A. —Intensity of light absorbed by the film. 



Curve B. — Photo current for unit intensity of light absorbed. 



Table II. 



Thickness of film 

 in secouds. 



Current from 



film. 



Light. 

 absorbed. 



Current per unit 

 light absorbed. 



50 



8 



6 



133 



80 



22 



10-5 



21 



100 



100 



13 



77 



130 



235 



16 



147 



150 



220 



21 



105 



200 



178 



31 



58 



240 



150 



41 



37 



In curve B (fig. 3) are plotted the photo currents per unit 

 absorption of light, against the thickness of film, and the 

 maximum value of the current appears still more pronounced. 

 The photoelectric sensitiveness of platinum is thus very 

 large for films of the order of 10~ 7 cm. 

 June 19, 1916. 



