PKOBLEMS ON REFRACTIVE INDEX 



a, 



A 



is the incident ray in air, F G the refracted ray in crown glass. The 

 angle A FE is the angle of incidence, BFG the angle of refraction. 

 Sine A F E divided by sine B F G is equal to the refractive in- 

 dex of air into crown glass, or, in other words, the absolute refractive 

 index of crown glass, /u ; thus in this particular case : 

 (Problem) I. : 



sin AJFJ^_ sin 45 _ -707 _ 3^ _ 

 sin B F G ~~ sin~28 ~~ -472" ~ 2" = ^' 



This problem, however, is not actually needed by the reader of 

 this book, for a table of 

 absolute refractive indices 

 is given in Appendix B. 



It will be clear from 

 the above that when the 

 refractive index, absolute 

 or relative, of a ray from 

 any first medium is given, 

 the refractive index from 

 the second to the first may 

 be found. 



Thus, the absolute re- 

 fractive index p from air 

 into glass being given as 



'-, find n f , the refractive 



index from glass into air. 



(Problem) II. : 

 , 1 1 2 



** ~ =o = . r 

 H 6 3 



2 



When the absolute 

 refractive indices of any 

 two media are given, the 

 relative refractive indices 

 between the media can be 

 found. 



Thus, the absolute re- 

 fractive index p of crown 

 glass is 1-5, and the ab- 

 solute refractive index // 

 of flint glass is 1*6 ; find the relative refractive index //' from crown 

 to flint. 



G- 



FIG. 2. The normals to a plane and a curved 

 surface. 



(Problem) III. : 



= HJ = 



JL 1*5 



The relative refractive index 

 by (problem) ii. : 



" 



1-066 



from flint to crown is determined 



= -938. 



