RAINBOW. 



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rays which enter at the top of the rain- 

 drops, refracted from the bottom : 



But in the other bow we see the rays 

 which enter at the bottom of the rain- 

 drops (after two reflections), refracted 

 from the top. 



Here A, B, C, represent three drops of rain in the 

 PRIMARY (or inner) RAINBOW. 



The least refracted line is RED, and BLUE the most. 



So the RED ("or least refracted rays) of all the drops 

 in the position of A, the YELLOW of those in the 

 position of B, and the BLUE (or the most refracted 

 rays) of the lowest drops, all meet the eye D, and form 

 a rainbow to the spectator. 



The reason why the primary how exhibits the 

 stronger colours is this because the colours are seen 

 after one reflection and two refractions ; but the colours 

 of the secondary (or upper) rainbow -undergo two 

 reflections and three refractions. 



