Double rainbows are not only rare but also one of the extraordinary phenomena created by nature.
On the evening of July 22, many residents in Hanoi witnessed a fascinating natural phenomenon when a vibrant and distinct double rainbow appeared in the sky.
Double rainbow appearing in the sky of Hanoi on the evening of July 22 (Photo: Triều Dương).
A double rainbow is not only a rare sight but also one of the remarkable phenomena brought about by nature. Typically, a rainbow occurs when sunlight shines through raindrops, causing refraction and dispersion. Longer wavelengths (red) are bent more than shorter wavelengths (blue), resulting in a bright rainbow in the sky.
The phenomenon of a double rainbow, also known as a “twin rainbow,” occurs when sunlight reflects “a second time” off raindrops, creating a second arc on the same plane as the primary rainbow. Light enters the raindrop and refracts at the surface; instead of escaping after hitting the back of the raindrop, it refracts a second time, forming the secondary rainbow.
The distinctive feature of the secondary rainbow is that its colors are inverted compared to the primary rainbow. The light from the secondary rainbow is also fainter and harder to see due to the significantly reduced amount of light that undergoes the second refraction. The shape and position of the secondary rainbow differ as well, appearing about 10 degrees away from the primary rainbow and radiating at an angle of 50 degrees.
Double rainbows are very rare, so those who have the opportunity to witness this phenomenon are considered extremely lucky. In some Eastern cultures, double rainbows symbolize good fortune and happiness.
