Radiant Heat and Light 



133 



face at a slant, it reflects at the same slant in the oppo- 

 site direction. 



But to reflect light directly and to give a clear image, 

 the surface the light strikes must be extremely smooth, 

 just as a tennis court must be fairly smooth to make 

 a tennis ball rebound accurately. Any surface that is 

 smooth enough will act like a mirror, although naturally, 

 if it lets most of the light go through, it will not re- 

 flect as well as if it sends all the light back. A pane 

 of glass is very smooth, and you can see yourself in it, 

 especially if there is not much light coming through 

 the glass from the other side to mix up with your re- 

 flection. But if the pane of glass is silvered so that 



FIG. 63. In the same way, the light bounces (reflects) from one boy to the other. 

 It does not return to the point from which it started and neither boy can see 

 himself. 



