THE RAINBOW 101 



Experiment 36. Refraction and Dispersion. 

 Apparatus: Triangular glass prism 60, one-inch face, 

 three inches long. 



a. Place prism on its end, on piece of note paper, and draw 

 pencil line around it. Now draw a straight line, three inches 

 long, up to one face of the prism at an angle of about 45. 

 Looking through that side of the prism through which the line 

 would come out, if continued, lay a rule in line with the pencil 

 line as seen through the prism. Draw a line along the rule, 

 remove the prism and connect the ends of the two long lines 

 by means of a short one across the outline of the prism. The 

 complete broken line indicates the path of light through the 

 prism. Which way is it bent ? 



b. Go near a window, and pull down the curtain so that 

 only a narrow beam of sunlight enters the room. Hold the 

 prism in this beam until you see the prismatic colors. Which 

 color is bent the most ? How many colors can you distinguish ? 

 Name them. 



73. THE RAINBOW 



The rainbow is well named, as it is composed of raindrops 

 which occupy positions in the arc of a circle. A rainbow has 

 no existence ; that is, it is a condition, t and raindrops which 

 are in the proper position at one instant pass out of that 

 position the next instant, to have their places occupied by 

 other raindrops. 



Each drop of water which takes part in the production of a 

 rainbow acts similarly to the prism in Experiment 36. All 

 combined, they give the impression of bands of colors. Every 

 drop of water which sends a certain kind of waves to the eye 

 is at an equal distance from the eye. Now all points which 



