114 LIGHT 



a smooth surface ab, such as glass, still water, polished 

 metals, etc., each ray is reflected at the same angle as 

 all the others, and thus their positions among each other 

 are unchanged. These reflected rays would form an 



image of the object, as ef. 

 Fig. 84 may serve to show 

 how such rough surfaces as 

 snow, plaster walls, white 

 cloth, etc., may reflect light 

 waves which do not make 

 images. Rays from the ob- 

 ject c'd' strike the rough 

 surface a'b f ; each ray is of 



course reflected from the point where it falls, so as to 

 obey the law of reflection ; but as these points lie in 

 short lines of many directions, the rays will leave the 

 surface a f b r in various directions, forming no image. 



134. Mirrors and Reflectors Mirrors are smooth 



surfaces which reflect nearly all of the light waves 

 which fall upon them. Plane mirrors generally form 

 images which are erect and like the object. Standing 

 before a mirror, our image seems to be twice as far 

 away as the distance to the mirror; in other words, the 

 image appears just the same size as the object would 

 appear if it were twice that distance away. 



Rays striking a curved surface are reflected as if they 

 struck a plane which touched the curve at that point 

 only. Thus, in Fig. 85, parallel rays moving as shown 

 by arrows are turned off from the curved surface just 

 as if they had struck the straight lines back of the 



