COLOR 127 



and violet. Note that these are not all of the many colors 

 in white light, but only the more important groups. 



148. The Rainbow. After a shower, when the. air 

 still contains many heavy clouds, drops of water in 

 these clouds may serve to refract the sunlight passing 

 through them, and thus separate its several colors, like 

 the prism in 147. Thus there will appear reflected to 

 the eye of an observer a spectrum which will contain 

 the seven prismatic colors. This spectrum usually ap- 

 pears as an arc of a circle low down in the sky; it is 

 called a rainbow. 



149. Color of Light Waves. Waves from a luminous 

 source sometimes appear to change color after passing 

 through a substance ; a chimney of red glass seems to 

 give a red color to the rays from a lamp, or sunlight 

 seems blue after passing through blue glass. Now the 

 fact is not that color is given to the waves, but rather 

 that some of the waves are taken from the learn of light. 

 Red glass, for example, contains a substance which 

 absorbs (takes into itself) many of the waves that enter 

 it, allowing the red rays to pass on through ; in the 

 same way, blue glass allows mostly the blue waves to 

 pass through it. The sun often seems red at sunrise or 

 in setting. This is because its waves have to pass such 

 a long distance through the denser and dusty air near 

 the earth that many of the shorter waves are absorbed, 

 leaving mostly the red ones to pass entirely through. 



150. Colors of Objects. The color of luminous objects 

 depends directly upon the color of the waves they 

 send out. 



