Extraordinary weather phenomenon: the double rainbow

During rainy or stormy weather, rainbows are numerous. But the appearance is even more spectacular when it comes to a double rainbow, a more common phenomenon than you might think.

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There are several types of rainbows: first of all themain rainbow, also called primary arc which is most often visible during the passage of showers. Then the secondary arc, the double rainbow which is materialized by a second arc above the first. A third and even fourth arch can also be seen, although this is rare. But there are also white arcs that appear on a misty or foggy screen.

Rainbows can also be of solar or lunar origin. Among all these different amazing bows, the double rainbow is one of the most common. Although spectacular, it is actually always present if the first arc exists! This secondary arc is simply not always bright enough to be visible.

Inverted colors compared to the first

First characteristic of the double rainbow, its colors are reversed with respect to the first: in the primary arc, blue is on the inside of the curve and red on the outside. In the secondary arc, blue is on the outside and red on the inside. If a third arc occurs, the colors of the latter are then reversed with respect to the second arc, and therefore identical to the first arc.

The double rainbow is caused by a double reflection of the light from Sun inside raindrops. It appears in the opposite direction to the Sun, at an angle of 50-53° and always less luminous than the first. This second arc is less visible: while the first arc is generated by the reflection of sunlight at a 40-42° angle inside the raindrops, the second is visible thanks to the double reflection, which therefore results in less vivid colors.

The second is also much larger, almost twice as large as the first. The two rainbows are separated by a dark band, called the “dark band of Alexander”, an area where few solar rays are refracted.

A symbol of luck and transformation

In some cultures, the appearance of a double rainbow is linked to positive meaning, luck and transformation: in the East, the first arc represents the material world and the second arc is associated with the spiritual realm. While the double rainbows have been described and photographed for hundreds of years, it will be necessary to wait until 2011 to see the first photo appear of a third, then a fourth arc.

A perfectly visible double rainbow. © Sašina Kuhinja

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