306 



WELLS'S NATURAL PHILOSOPHY. 



considerable ; when the angle, or inclination is small, the 

 amount of light reflected will be diminished. 



Thus, for example, when light falls perpendicularly upon the surface of 

 glass, 25 rays out of 1,000 are returned; but when it falls at an angle of 

 85°, 550 rays out of 1,000 are returned. 



Thus, a surface of unpohshed glass produces no image of an object by re- 

 flection when the rays fall on it nearly perpendicularly ; but if the flame of a 

 candle be held in such a position that the rays fall upon the surface at a veiy 

 small angle, a distinct image of it will be seen. 



We have in this an explanation of the fact, that a spectator standing upon 

 the bank of a river sees the images of the opposite bank and the objects upon 

 \t reflected in the water most distinctly, while the images of nearer objects 

 are seen imperfectly, or not at all. Here the rays coming from the distant 

 objects strike the surface of the water very obliquely, and a sufBcient number 

 are reflected to make a sensible impression upon the eye ; while the rays pro- 

 ceeding from near objects strike the water with little obliquity, and the hght 

 reflected is not sufBcient to make a sensible impression upon the eye. 



This fact may be clearly seen by reference to Fig. 240. 



Fig. 240. 



Let S be the position of the spectator ; and B the position of distant 

 objects. The rays R and B R which proceed from them, strike the surface 

 of the water very obliquely, and the hght which is reflected in the direction 

 R S is sufficient to make a sensible impression upon the eye. But in regard 

 to objects, such as A, placed near the spectator, they are not seen reflected, 

 Jjecause the rays A R' which proceed from them strike the water with but 

 little obliquity ; and consequently, the part of their light which is reflected 

 in the direction R' S, toward the spectator, is not sufficient to produce a seo* 

 sible impression upon the eye. 



What is the 663. If an object be placed between two 

 pa?aiiei°*^pune V^^^^' mirrors, each will produce a reflected 

 mirrors? image, and will also repeat the one reflected 



by the other — the image of the one becoming the object 

 for the other. A great number of images are thus pro- 



=^7/ 



Iff- 



