1 66 Common Science 



The white cloth is white because it reflects all colors back 

 at once. It therefore absorbs practically no light. But the 

 reason the black cloth looks black is that it reflects almost 

 none of the colors it absorbs them all and changes them 

 to heat. The colored cloth reflects just the red or the 

 green light and absorbs the rest. 



Maybe you will understand color better if it is ex- 

 plained in another way. Suppose I throw balls of all 

 colors to you, having trained you to keep all the balls 

 except the red ones. I throw you a blue ball ; you keep 

 it. I throw a red ball ; you throw it back. I throw a 

 green ball; you keep it. I throw a yellow ball; you 

 keep it. I throw two balls at once, yellow and red ; you 

 keep the yellow and throw back the red. I throw a 

 blue and yellow ball at the same time ; you keep both 

 balls. 



Now suppose I change this a little. Instead of throw- 

 ing balls, I shall throw lights to you. You are trained 

 always to throw red light back to me and always to keep 

 (absorb) all other kinds of light. I throw a blue light ; 

 you keep it, and I get no light back. I throw a red light ; 

 you throw it back to me. I throw a green light ; you 

 keep it, and I get no light back. I throw a yellow light ; 

 you keep it, and I get no light back. I throw two lights 

 at the same time, yellow and red ; you keep the yellow 

 and throw back only the red. But yellow and red to- 

 gether make orange; so when I throw an orange 

 light, you throw back the red part of it and keep the 

 yellow. 



Now if we suppose that instead of throwing lights to 

 you I throw them to molecules of dye which are " trained " 



