Double rainbows are not as rare as you might think. They occur when the sun's rays are reflected twice inside a water droplet. The second reflection causes the light to be separated into two rainbows, with the secondary rainbow appearing fainter and larger than the primary rainbow.

The exact frequency of double rainbows is difficult to determine, as it depends on a number of factors such as the time of day, the angle of the sun, and the amount of water vapor in the atmosphere. However, it is estimated that double rainbows occur about one-tenth as often as single rainbows.

Here are some additional facts about double rainbows:

* The secondary rainbow is always dimmer than the primary rainbow, as some of the light is absorbed each time it reflects inside the water droplet.

* The secondary rainbow is always formed on the opposite side of the sky from the sun.

* The width of the double rainbow depends on the size of the water droplets. Smaller droplets produce wider rainbows.

* Double rainbows are often seen near waterfalls, fountains, and other bodies of water.

If you see a double rainbow, it is a beautiful sight to behold! It is a reminder of the beauty and wonder of nature.