Picture Alaska: Reflection Rainbows and how they form

Reflection rainbows are less common, as they require certain atmospheric conditions
KTUU's 70 years of broadcasting
Published: Jul. 18, 2023 at 1:56 PM AKDT
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ANCHORAGE, Alaska (KTUU) - The beauty of the natural world lies in the details.

Pulitzer Prize-winning journalist and science writer Natalie Angier is credited with the origination of this quote. While there are many ways one can research on the beauty of our natural world, none truly captures the essence of the saying than this quote.

Beauty is found all around us; from the blossoming growth of flowering plants to the elements paving a way through the earth and even to the rainbows that light up the sky following rain showers. Rainbows are truly one of the more mesmerizing sights that Mother Nature can put on display and depending on the conditions, one could see many types of rainbows.

As rain has been evident across Alaska for some time now, rainbows have become a common sighting where the sun has managed to peak through, and the way you view the rainbow is different from everyone else around you, as you’re seeing it put on display from a different angle.

So, what are the types of rainbows? What do they look like and how do they form?

It’s not rare to see a rainbow at all, but what is rare is the type of rainbow one may be seeing. But let’s get to the simple rainbow — or primary rainbow as it’s called. It’s the one we’ve come to know and love that beams across the sky in bright colors.

Fred McCormick captured this shot of a primary rainbow overlooking Dillingham
Fred McCormick captured this shot of a primary rainbow overlooking Dillingham(Fred McCormick)

You may be surprised to learn that a rainbow isn’t really an object and it doesn’t truly exist: It’s nothing more than an optical phenomenon caused by sunlight and atmospheric conditions. Most rainbows appear during or after rain showers and are always opposite the sun.

In order for a rainbow to form, light must enter a water droplet. In doing so, it bends as the light moves from air to denser water. As the light reflects off the inside of a droplet, it separates into the colors we’ve come to know in the rainbow as ROY G. BIV (Red, Orange, Yellow, Green, Blue, Indigo and Violet). While other colors are present in the rainbow, these are the colors most commonly seen to the naked eye.

A full rainbow actually forms a complete circle — however, from the ground, we see only a part of it. It’s only when we’re flying high in the sky can we see that the rainbow itself is an entire circle.

It truly is one of Mother Nature’s grander displays and sometimes the atmospheric conditions can take it one step further.

Enter the double rainbow.

Rachel Dillon captured this shot of a Double Rainbow in a hotel parking lot in Fairbanks.
Rachel Dillon captured this shot of a Double Rainbow in a hotel parking lot in Fairbanks.(Rachel Dillon)

There you are staring at the awe-inspiring rainbow that’s sweeping across the sky when you see what looks like another rainbow doubled up on the first. This is called a double rainbow, or a more scientific term, secondary rainbow. You may have noticed that it’s significantly dimmer and that’s because the process that must occur for a secondary band to form.

We’ve established that the primary rainbow is caused by the reflection inside the water droplet, so what causes the secondary bow? The secondary bow is nothing more than a secondary reflection that is caused inside the water droplet, which is then re-reflected at a different angle. Due to this angle difference, the secondary rainbow appears above the primary rainbow and has its colors reversed.

Did you know that the sunlight must strike the raindrop’s edge at a certain angle in order for a rainbow to form? Not only that, rainbows get their shape due to the spherical waterdrops that they reflect off of.

How about we take it one more step forward and add additional details into the mix for Mother Nature. If all of the right conditions are present, one could even see what could be mistaken as a triple rainbow, when in fact it’s a reflection rainbow.

Fred McCormick captured this reflection rainbow overlooking Dillingham.
Fred McCormick captured this reflection rainbow overlooking Dillingham.(Fred McCormick)

While it’s hard to see the reflection rainbow as vividly as the primary rainbow, remember that with each successive pass that the light must make, the bows grow fainter. It’s also important to note that rainbows appear more vibrant against darker backdrops than with clearing skies in the background.

So what is a reflection bow and how do they form? In order for a reflection bow to form, one must be near a body of calm water or very wet soil. A reflection rainbow is nothing more than a reflection of the sunlight from a body of water and not through the raindrops themselves. The bow is most commonly seen stretching up from the primary bow, as depicted in the picture above.

Reflection bows are unique in that they appear to come from below, rather than above. This is simply due to the nature of the sunlight being reflected from the calm body of water as its origination source. Think about how one can look at a calm body of water and instantly be blinded by the sun’s reflection. It’s this reflection that causes the bow.

Mother Nature can even take it a step further, although it is exceptionally rare to find a triple or quadruple bow. Not only would you need every condition to be ideal, but you would have to look towards the sun in order to see these very rare optical phenomena.