SCIENCE OF COMMON THINGS. 



257 



Production and explanation of the rainbow 



of the different colors, generally exhibited upon the 

 clouds during the occurrence of rain in sunshine. 



If we take a glass globe filled with water, and suspend it at a certain 

 height in the solar rays above the eye, a spectator standing with his back 

 to the sun will see 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 different heights presenting to the eye the seven primitive colors 

 iri succession. If now, in the place of the globe occupying different posi- 

 tions, we substitute drops of water, we have a ready explanation of the 

 phenomena of the rainbow. 



Fig 70. 



Let -A, B, and C be three drops of rain ; S A, S B, and S C, three rays 

 of the sun. A is divided into three colors ; the blue and yellow are 

 bent above the eye, D, and the red enters it. 



The ray, S B, is divided into three colors ; the blue is bent above the 

 eye, and the red falls below the eye, D, but the yellow enters it. 



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

 bent most) enters the eye ; and the other two fall below it. Thus the 

 eye sees the blue of (7, and of all drops in the position of C; the 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 ; and thus it sees a rainbow. 



1683 What is the occasion of the rainbow f 



The rainbow is produced by the refraction ana re- 

 flection of the solar rays in the drops oi falling rain. 



1683 What are the conditions necessary in order that we may see a 

 rainbow f 



The rainbow can be seen only when it rains, and in 

 that point of the heavens which is opposite to the sun. 

 It is necessary also that the sun should not have too 



