Secondary rainbow

From Glossary of Meteorology

secondary rainbow

Distinguished from other rainbows by its angular radius, color order, and brightness.

The bow is seen between about 50° and 54° from the antisolar point (shadow of the observer's head) or, equivalently, between 130° and 134° from a light source (such as the sun). Reds are found to the inside of the bow (closest to the primary bow) with the blues to the outside. The secondary bow is usually dimmer than the primary bow. Any theory of the bow that approximates the behavior of light as a ray attributes the secondary bow to light that has undergone two internal reflections. The losses accompanying the additional reflection account for the bow being fainter than the primary bow. This may mean that the bow has insufficient contrast to be distinguished from the background. It is sometimes incorrectly asserted that the extra reflection, by itself, is responsible for the reversal of colors from those of the primary bow.
See also rainbow, supernumerary rainbows;
compare primary rainbow.

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