Upper: Light path of main rainbow
Lower: Light path of sub-rainbow
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This image shows you the excellent rainbow which appeared in the east sky right after the shower early summer in 1986.
A rainbow is the atmospheric optical phenomenon observed by solar light's being reflected and refracted by the round water drops floating in the air.
The center of the rainbow's arc is equivalent to the opposite position of the sun, and its radius is about 42 degrees.
The sunlight passes in the drop as the upper figure shown.
Because the refraction angle varies in the wavelength of the light, rainbow seems divided into seven colors from inside blue to outer red.
And this picture shows that there is one more very faint rainbow on the right of the main rainbow.
It's called the "Sub-rainbow". This is observed by solar light that reflects twice in the water drops as the lower figure shows you.
The sub-rainbow has the radius of about 51 degrees, and its color looks red inside and blue outside, reverse to the case of main-rainbow.
The light of sub-rainbow is very dimmed because it's light has been reflected in surplus in water drops, you cannot observe the sub-rainbow clearly unless you have extraordinary good conditions.
Other images of Rainbows
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