PHENOMENA OF LIGHT 179 



fleets some waves (colors) more largely than others, and ab- 

 sorbs the different color elements incident upon it in vary- 

 ing proportions. 



Repeat the tests, using in turn cards of different colors. 

 (Get as nearly pure colors as can be had.) Explain the 

 results as phenomena of selective absorption. 



Explain (a) the green of the grass ; (b) the yellow of gold ; 

 (c) the white of any painted house. 



6. With a piece of blue (cobalt) glass so held that light 

 from the window comes through it to you, explain selective 

 transmission. In like manner use a piece of red glass, and 

 explain. 



Now put the two pieces of red and blue glass together, 

 and between you and the light from the window. Account 

 for the results. 



Observe the spectrum on the screen as first the blue glass 

 is put near the prism in the path of the emergent rays, then 

 the red glass, and then both glasses. What is the explana- 

 tion of these results ? 



