of Light by thin Layers of Metal. 



461 



Here the observations contained in a horizontal series all refer 

 to the same metallic layer. Accordingly theory would require 

 that the values of the constant e should be identical in both 

 cases (reflection in air and reflection in glass), and that the quo- 



Q 



tient of — should be equal to the exponent of refraction fi of 



. d . 



glass, given in the last column. These requirements of theory 



are evidently only very imperfectly fulfilled — which necessitates 

 the assumption that, in consequence of a different molecular 

 constitution of the metallic surfaces adjacent to air and to glass, 

 the constants of reflection assume somewhat different values. 

 Similar are the results of the series of observations given in § 43, 

 for the reflection-constants of the same silver surfaces in air, 

 water, and oil of turpentine : — 



e 1 = 87°24', 

 ^ = 0-5178, 



^=1-234, ^=1-336, 



e 2 =87°52', 

 Z(9 2 = 0-4264, 



6 



<? 3 = 86° 9', 

 7^3=0-3595. 



£ =1-440, ^ 3 =l-474. 



With regard to transparent metallic layers the first question 

 is, whether the degree of transparency required by theory agrees 

 with that found by experiment. As the factor D 2 is contained 

 in the expression for the intensity of the ray after transmission, 

 that factor must first be determined. With the aid of the above 

 given optical constants of silver for Fraunhofer's lines D and H, 



the values contained in the following Table, of ^y 2 for various 



thicknesses of silver, are easily calculated on the supposition of 

 perpendicular incidence : — 





Fraunhofer's line 





Fraunhofer's line 



A. 







A 







D. 



H. 





D. 



H. 



millim. 







millim. 







001 



1-830 



1786 



006 



37-53 



32-53 



•02 



3 348 



3-192 



•07 



68-67 



58-10 



•03 



6-126 



5-702 



•08 



125-66 



1038 



•04 



11-21 



1019 



•09 



229-9 



185-4 



•05 



20-51 



18-20 



•10 



420-7 



331-2 



When, further, we set up the actual intensity-expression for 

 the ray which has passed through the system of silver and flint 

 glass, in which the loss of intensity in the passage through the 

 uncoated surface of the glass also comes into consideration, we 



