382 



REFLECTION OF LIGHT. 



FIG. 282. 



A, draw Aa perpendicular to MN and make ad equal to Ad. Then 

 will a indicate the position of the image 

 of A. From B, draw Bb perpendicular 

 to MN and make be equal to Be. Then 

 will b indicate the position of the image 

 of B. By connecting a and b we locate 

 the image of AB. Draw aE, bJS, Ao 

 and BL AoE represents one ray of the 

 cone of rays from A that enters the eye ; 

 BiE represents one ray of a similar cone 

 from B. Draw a similar figure on a 

 larger scale, representing the eye at C . 



Test your figure by seeing if the angle of incidence is equal to the 



angle of reflection. In all such constructions, represent the direction 



of the rays by arrow-heads, as shown in Fig. 282. 



598. Multiple Images. By placing two mirrors 

 facing each other, we may produce multiple images of 

 an object placed between them. Each image acts 

 as a material object with respect to the other 

 mirror, in which we see an image of the first 

 image. When the mirrors are placed so as to form an 

 angle with each other, the number of images becomes 

 limited, being one less than the number of times that the 

 included angle is contained in four 



right angles. The mirrors will give 

 three images when placed at an angle 

 of 90; five at 60 ; seven at 45. 



(a.) When the mirrors are placed at right 

 angles the object and the three images will 

 be at the corners of a rectangle as shown at a 

 A, a, a' and a". FlG - 28 3- 



599. Concave Mirrors. A spherical concave 

 mirror may be considered as a small part of a spherical 

 shell with its inner surface highly polished. Let MN (Fig. 

 284) represent the section of such a concave spherical mir- 



