Atmospheric Optical Illusions - 89 
water droplets exposed to sunlight at the correct angles. The 
fine spray of a hose, or the drops of a distant thundershower 
show the rainbow alike. The distance of the drops from the 
observer makes no difference in the appearance of the rain- 
bow, whether the distance is only a few feet or many miles. 
When sunlight strikes a raindrop it enters into it, is re- 
fracted and reflected around inside the drop several times 
REFLECTED 
ON INNER 
SURFACE 
VIOLET 
SE 
OPTICS OF RAINDROP 
and finally is permitted to pass out of the drop again. How- 
ever, the light which escapes from the raindrop has been dis- 
persed, that is, has been broken up into its spectral colors, 
and its direction is also different from the direction of the 
original sunlight ray. What is more, since most of the light 
of a particular color is reflected at some specific angle to the 
direction of the incident sunlight, it is concentrated. So if you 
are in one position with respect to the sun and a particular 
