XLVII. Physiological optics, applied, a. The application 



of the laws of refraction to the mammalian eye. 



b. To locate in the mammalian eye 



the cardinal points of the sim= 



pie dioptric system. 



The dissection of the ox eye revealed several refractive 

 media (cornea, aqueous humor, lens, and vitreous humor) 

 and several curved surfaces bounding these media. In 

 determining the focal distance of a lens one must know the 

 radius of curvature and the refractive index. In determin- 

 ing the focal distance of a system of refractive media and 

 surfaces one must know (1) the radius of curvature of each 

 surface, (2) the refractive index of each medium, and (3) 

 the location of their cardinal points upon the principal 

 axis of the system. 



The mammalian eye receives its light through media 

 and surfaces, as indicated in the following table: 



This array of media and surfaces would seem to make 

 a problem too intricate to solve with the means at our dis- 

 posal. Notice, first that the tear film and the ant. and 

 post, corneal surfaces have the same radius of curvature; 



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