NATURE OF LIGHT 113 



From this experiment we may learn the Law of 

 Reflection: The angle at which rays leave a surface is 

 equal to that at which they strike it. 



Experiment 89. Hold a small mirror before you, just below 

 the eyes, about ten inches away, with its glass side facing away 

 from you. In the other hand hold another mirror a few inches 

 farther away, an inch or two higher than the first, and facing 

 you. Look over the first into the second ; with a little care these 

 may be so placed that you will see several reflections of your 

 eyes. This shows that reflected waves may be again reflected 

 many times. 



133. Reflection from Different Surfaces. Light waves 

 from the same source may fall upon different objects and 

 there be so treated ^ 

 that the objects will 

 present a variety of 

 appearances to the 

 eye. For example, 

 rays from the sun may FlG - 



fall upon several bodies : one of these may appear to be 

 green, another red, a third may seem dark, and still 

 another very bright. Yet they are all seen by means of 

 rays which come from one source. These differences 

 are due to the different behavior of substances toward 

 light waves ; many give off only a part of the waves 

 that fall upon them, and their appearance to the eye 

 depends upon what waves they give off. 



But among surfaces which reflect nearly all of the rays 

 that strike them, there is still a difference ; some reflect 

 regularly and others reflect only scattered light waves. 

 When parallel rays from an object cd (Fig. 83) strike 



