REFLECTION 331 



of reflection. The angle of reflection always equals the angle of 

 incidence. 



Kinds of Mirrors. Mirrors are divided into two classes, plain and 

 curved. The curved mirrors are redivided into two types, the 

 concave and the convex. The mirrors may be spherical concave 

 or cylindrical concave or convex. The concave spherical mirror is 

 used for reflecting light upon the teeth, into the throat, and into the 

 ear. It is also used in headlights and for reflectors of lights. The 

 inside and outside of a silver spoon furnish good examples of mirrors 

 of this type. Find other examples about your home. 



FIG. 202. 



The convex spherical mirror is used on automobiles so that the 

 ^driver may see the road behind without turning his head. 



Parabolic Mirrors. Mirrors are sometimes constructed so as to 

 produce a parabolic surface. This causes the rays of light which 

 are reflected from the mirror to travel in parallel rays. This reflector 

 is used in automobile lamps, searchlights, headlights of locomotives, 

 bicycle lanterns and carriage lamps. The light is placed at the prin- 

 cipal focus of the mirror. 



QUESTIONS 



1. What kind of an image do you see in polished sheet iron? 



2. Why do you see an image when you look at the metal? 



