COLOR 125 



fall upon it. Also we know that any illuminated body- 

 is seen by means of such waves as fall upon it and are 

 reflected to the eye. Thus it is clear that the color of 

 any object depends upon what waves it sends to the 

 eye, and that color itself is a property of the light 

 waves. 



* Sound waves, we recall, vary greatly in their rate of 

 vibration, and the resulting difference in sounds is 

 called pitch. In the same way light waves differ 

 greatly in rate of vibration; the effect of these differ- 

 ent vibration rates upon the eye is that the waves have 

 different colors. In other words, the color of a light wave 

 depends upon its rate of vibration. For example, red 

 waves have a low vibration rate, green a higher rate, 

 while violet waves vibrate about twice as fast as red ones. 



146. White Light. Just as sound waves of many 

 different vibration rates may travel together from a 

 vibrating body to the ear, so light waves of many colors 

 may mix together in one beam of 

 light. The color of the learn as a 

 whole might be very different from 

 that of any single wave, just as 

 the pitch of a noise is unlike that 

 of any one tone in the noise. 



Experiment 96 Paste pieces of col- 

 ored paper (violet, green, and red) on a * 

 circular cardboard, as in Fig. 98. Loop a stout string through 

 the two holes near the center ; twist this string so as to rotate the 

 card rapidly (any boy knows how). What color does it seem to 

 be while rotating? Do the same with other colors two or more 

 at a time. 



