Mystery of a double rainbow revealed

WASHINGTON - Twitter was in a flurry over a double rainbow that formed over Los Angeles last night.

“And L.A. peeps, did you see the amazing double rainbow? I don’t wanna be ‘double-rainbow’ guy, but that was spectacular. Almost worth the rain,” ABC News quoted actor Jason Alexander as tweeting.

How is a double rainbow made?

“The sun needs to be at a low angle. Usually, the magic number’s actually 42 degrees above the horizon or less. The sun would also need to be at your back and the rain at the front,” said Mike Pigott, an AccuWeather meteorologist.

Two laws of physics - reflection and refraction - are at work to produce a rainbow. Pigott said a double rainbow is formed when there are two reflections inside a raindrop.

“In the case of a secondary rainbow, you’d still have the primary rainbow — you’d have that first reflection at 42 degrees. But the sun’s rays can also have a second reflection off the back [of the raindrop]. So instead of reflecting off the back once, it will actually reflect twice. And that’s typically at a different angle,” he said.

The secondary rainbow is fainter, but more colourful in the reverse order.

“In the case of L.A., this would certainly be perfect because the clouds were clearing out from that heavy rain,” said Pigott.

“The sun would be setting in the West and the rain would be moving off to the East, and L.A. would be dead in the middle.”

In fact, double rainbows are not such a rare phenomena. Kevin Garrett, a physical scientist with the National Oceanic and Atmospheric Association, said that sixth order rainbows are even possible. (ANI)