334 



WELLS'S NATURAL PHILOSOPHY. 



What experi- 

 ments prove 

 the decomposi- 

 tion of light by 

 drops of wa- 

 ter? 



C95. Rainbows are also formed when the sun shines upon drops of watei 

 falling in quantity from fountains, waterfalls, paddle-wheels, etc. 



That the rainbow results from the decomposition of the solai 

 rays by drops of water, may be proved by the following sim- 

 ple experiment: — If we take a glass globe filled with water, 

 and suspend it at a certain heiglit in the solar rays above the 

 eye, a spectator standing with his back to the sun will seo 

 the refraction and reflection of red light; if, then, the globe be lowered 

 slowly, the observer retaining his position, the red light will be replaced 

 by orange, and this in its turn by yellow, and so on, the globe at dif- 

 ferent heights presenting to the eye the seven primitive colors in succession- 

 If now, in the place of the globe occupying different positions, we sub- 

 stitute drops of water, we have a ready explanation of the phenomena of 

 the rainbow. 



Drops of rain, suspended to grass or bushes, may be frequently found to 

 appear to the eye of a bright red; and by slightly changing the position of tho 

 eye, the colors of the drop may be made to appear successively yellow, green, 

 blue, violet, and also colorless. This also proves that rays of light, faUing in 

 certain directions upon drops of water, are refracted thereby and decomposed 

 into colored rays that become visiblo to the eye when it is situated in the 

 proper direction. 



Fig. 2G9, 



The principles of the 

 formation of the rain- 

 bow may be further 

 illustrated by Fig. 2G9. 

 Let A B and C be three 

 drops of rain ; S A, 

 S B, and S C, three 

 rays of the sun. Tho 

 ray S A, by refraction, 

 is divided into three 

 colors ; the blue and 

 yellow are bent above 

 the eye, D, and tha 

 red enters it. 



The ray, S B, is di- 

 vided into three col- 

 ors ; the blue is bent above the eye, and tho red falls below the eye D, but 

 tho yellow enters it. 



The ray, S C, is also divided into three colors. The blue (which i3 

 bent most) enters the eye, and the other two fall below it Thus tho 

 eye sees the blue of C, and of all drops in the position of C ; tha 

 yellow of B, and of all drops in the position of B; and the red of A, 

 and of all drops in the position of A. The same may be also inferred 

 respecting the other four colors of tho spectrum; and thus tha eye 8ee» 

 a rainbow. 



