THE ANALYSIS OF LIGHT. 



325 



Explain more 

 fully tho action 

 of the comtlx 

 leiis in tliis re- 

 spect? 



naked eye, by causing a greater number of rays of light 

 proceeding from them to enter the eye. 



The lighb which produces vision, as ■will bo more fully ex- 

 plained herealler, enters the eye through a circular opening 

 called the pupil, which is tho black circular spot surrounded 

 by a colored ring, appearing in the center of tho front of tho 

 eye. Now, as the ra^^s of light proceeding from an object 

 diverge or spread out in every direction, the number which will enter tho cyo 

 frill oe hmited by the size of the pupil. At a great distance from an object, 

 at will be seen in Fig. 2G5, few rays will enter the eye; but if, as in Fig. 2G6, 

 we place before the eye a convex lens of moderate size, a large number of 

 the diverging rays will be coUected and concentrated into a single point or 

 focus behmd it, and thus aBbrd to the eye occupying a proper position suffi- 

 cient light to enable it to see the distant object distinctly. 



FiCt. 265. 



Fig. 266. 



In like manner a concave mirror, by causing divergent rays which fal) 

 upon the surface to become convergent, may be used to produce the same ef- 

 fect, as is shown in Fig. 267. 



Ftc. 2G7. 



SECTION III. 



THE ANALYSIS OF LIGHT. 



685. It has, up to this point, been assumed, that light is a simple substance, 

 and tliat all its rays, or parts, are refracted in precisely the same manner, and 

 therefore suffer the same changes when acted upon by transparent media. 

 This, however, is not its constitution. 



