136 



HOW WE USE LIGHT 



line, and that if you put an opaque object in front of 

 the source of light, it will cut off the light and pro- 

 duce a shadow. A shadow is that space from which 

 light is cut off. The dark outline we cast on the pave- 

 ment when we stand 

 near a street lamp we 

 often call a shadow. 

 But remember a shadow 

 is not just a dark sur- 

 face, it is all the dark- 

 ened space back of 

 the object which cuts 

 off the light. Were 

 this not so, we could 

 not enjoy the shade 

 (shadow) of a tree hav- 

 ing dense foliage on a 



Where is the shadow? Is the word "shadow" bright hot day in the 



put in the correct place in this cut ? 011^*. 



o Ulillllcl . 



Reflection of Light. Light, such as a candle flame, a 

 red hot iron, a burning match, or the stars may come to 

 our eyes direct from its source. Bodies which give off 

 light of their own are luminous bodies. Very few of the 

 objects we see in the course of the day are bodies that have 

 light of their own, but we cannot see any object unless 

 light comes from it into our eyes. All nonluminous 

 bodies which we see receive light from some other source 

 and reflect it. That which is reflected into our eyes makes 

 the object visible to us. Do you realize how important 

 reflection of light is ? Without it you could not read, see 

 pictures, nor recognize friends by sight. You could not 

 see the moon nor yourself in a mirror. Sunlight which 

 enters your room may be reflected from one surface to 

 another many times before it is reflected by the particular 

 object you may be looking at. 



