LIGHT 277 



and refracted again as it leaves the drop. Since red is not 

 refracted so much as violet, the drop throws first to our 

 eyes red and then the other colors of the spectrum, ending 

 with violet from the position z>'. As the drop falls fromY, 

 it does not cast any color into the eye at E. 



The distance of the falling drops from the eye is what 

 determines the height of the rainbow. The reason that 

 the rainbow is an arc of a circle is because every drop 

 that throws the colors to the eye must be in a certain 

 position with respect to the eye. If a line is drawn from 

 the eye to the center of the circle of which the rainbow 

 is a part, all of the drops of water, while passing through 

 the rainbow are equally distant from the eye and any 

 point on the line. This line drawn from the eye to the 

 center of the circle of which the rainbow is an arc 

 forms an angle of 40 with the line drawn from the 

 eye to the violet color of the rainbow, and an angle 

 of 42 with the line drawn from the eye to the red part 

 of the rainbow. If a person were on top of a very 

 high building it would be possible to see almost the 

 complete circle of the rainbow. While standing on the 

 ground, where it is level or nearly so, not quite one- 

 half of the circle can be seen. 



No two persons can see exactly the same rainbow, be- 

 cause the eyes must be at a given angle from the drops 

 that make the colors. When a person moves, the rain- 

 bow moves also. If we move toward the rainbow, it 

 may keep at about the same distance from us as 

 when we started, depending upon how fast the cloud 

 is moving. 



A rainbow spectrum can be made with a street sprinkler, 

 hose, or sprayer in the morning or afternoon when the 

 sun is shining. Glass prisms on lamps, angles in glass 



