LIGHT. 19 



it will glance off with the same degree of ob- 

 liqueness in the other direction. Light is re- 

 flected from plane surfaces in the same manner. 

 This reflection is illustrated in the figure, 

 which represents a mirror, and a ray of light 

 falling upon it and again re-fleeted. 



25. APPARENT PLACE CHANGED BY RE- 

 Explam the FLECTIO N. As we always seem to see an 



change of ap- 



parent place object in the direction from which its rays 



by reflection. . , . . . 



enter the eye, a mirror which changes the 

 direction of the rays will change the apparent place 

 of the object. Thus, if the rays of the sun fall oblique- 

 ly upon a mirror, and are reflected to the eye, we shall 

 seem to see the sun in the mirror, in the direction 

 which the rays have acquired after reflection. 



26. CONCAVE MIRRORS. 

 Tf tirZl On considering that rays are 

 converge rays reflected from plane surfaces 



with the same degree of ob- 



liquity with which they fall upon them, 



we shall be able to comprehend how it is 



that concave mirrors have the property of converging 



rays of light, or bringing them together in a point. 



A number of small plane mirrors, situated obliquely 

 toward each other, as represented in the figure, and as 

 they might be arranged in a bowl or saucer, would 

 evidently have this effect. As a concave mirror may 

 be regarded as made up of innumerable plane mirrors, 

 similarly arranged, it would obviously be productive of 

 the same effect. 



