How Rainbows Are Formed

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In this week's Weather Wise Forecaster Kelley Smith and Meteorologist Dave Fraser explain how rainbows are formed.

Many residents love trying to catch a glimpse of the beautiful colors that hang in the clouds after a storm. One Helena resident says she captures them whenever she get's the chance,

"I take pictures of them. I take pictures of storms and after the storms and sunsets, everything like that. I'm kind of a rainbow chaser, I like to call it."

Meterologist Dave Fraser says what causes rainbows is water and light, which is why they appear after storms.

He says, "When light passes through a raindrop it's just like passing through a prism. It breaks up the light into different spectra so you see a rainbow just like you would through a prism."

And in Montana the conditions are ripe for seeing this natural phenomena. 

"We have perfect conditions for the formation of rainbows. We have a lot of sunshine. We have clear skies and of course in the spring and summer we have rain so it's the perfect combination of those three things."

It also makes for the perfect conditions for seeing the elusive double rainbow.

"I have seen several. I live in Kalispell and I see them to the east in the mountain ranges", says one Montana resident.

Fraser says the "double" in the name double rainbow explains a lot about how they're formed.

"A double rainbow is when light passes through a raindrop. Not all of that light is released to form the primary rainbow, some of that light is captured within the drop and it's released to form the primary rainbow, some of that light is captured within the drop and it's released as a secondary rainbow at a slightly different angle."

So next time it rains try to spot a rainbow, and if the light is right, you might just see a double rainbow. And now you're a little more Weather Wise.



Story by Dave Fraser, Beartooth NBC.
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Copyright ©2013 Beartooth Communications Company. All Rights Reserved.

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A shot of a rainbow in Helena taken in June

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Tagged as:

Weather Wise, Dave Fraser, Kelley Smith, Rainbows, rainbow chaser, water and light, light passes through a raindrop, natural phenomena, Prism

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