Second Surface of a Thin Plane Parallel Plate. 



29 



negative value o£ I would have been obtained. The silver 

 iodide was screened from light as much as possible, and test 

 readings showed that sensibility o£ the films to light was not 

 an appreciable source o£ error. The agreement is very satis- 

 factory, when we consider how imperfectly the mathematical 

 conditions are realized experimentally. The auxiliary functions 

 a, /?, 7 used in the calculation are given, also the difference 

 between the observed and calculated values. I was 1"40 X. 



Observations on Silver-Iodide Film. 



42 30 



44 



45 30 



47 



48 30 



50 



51 30 



53 



54 30 



56 



57 30 

 59 

 00 30 

 62 



-13. 



o 



311 

 394 

 461 

 50-7 

 54-2 

 57 

 597 

 611 

 626 

 640 

 652 

 66-2 

 671 

 68-0 



6-8 

 9-2 

 11-6 

 13-6 

 15-4 

 17-1 

 18-8 

 19*7 

 210 

 22-1 

 233 

 24 -2 

 252 

 262 



o 



15-5 

 21-0 

 251 

 28-2 

 31-2 

 32-3 

 343 

 365 

 35-9 

 36-9 

 372 

 36-4 

 39-2 

 367 



A'. 



A. 



o 



o 



63-9 



61-3 



75-2 



732 



810 



80-2 



840 



82-8 



84-8 



85-1 



848 



828 



82-4 



82-1 



799 



82-1 



76-8 



76-4 



78-2 



74 



68-2 



70-0 



644 



640 



59-8 



64-8 



553 



56-7 



A'-A. 



4-2-6 



+2-0 

 +0-8 

 4-14 

 -0-3 

 + 2«» 

 +0-3 

 __2'2 

 +0-4 

 -0-8 

 -is 

 4-04 

 -50 

 -1-4 



The rigorous formula becomes much more complicated in 

 the case of the silver film. Even when we make several 

 approximations, it is still impracticable and not so instructive 

 as the method used. In the case of silver, as in silver iodide, 

 we have a number of repeated reflexions in the film, but as the 

 silver absorbs light we shall disregard all but the first. 



Air 



Consider the vector polarized at right angles to the plane of 

 incidence. Let p s be the ratio of the amplitude of the reflected 



