Many people love seeing a rainbow when it occurs. Rainbows are not only beautiful and fantastic displays of the master artist’s art work, they are fascinating, too. Many people don’t stop to think about the wonder behind rainbows when they see one, so it can be interesting to look at a few facts about them.
* Rainbows are most often seen during or just after a rainfall, when there are a lot of tiny water droplets in the air. However, rainbows can also appear in fog, clouds or when there are crystals of ice in the air. Both water and sunlight are needed to make a rainbow, though, regardless of the state of the water.
* In order for a rainbow to be seen, sunlight must be refracted by almost exactly 42 degrees to the eyes of the observer. The water or ice crystals act as billions of tiny prisms to refract the light, but it still needs to be 42 degrees of refraction. If the angle is too great or too small, no rainbow is seen, even if the other conditions are perfect for one. Additionally, to see a rainbow, the sun must be behind you and the water droplets or ice crystals need to be in front of you.
* Since the rainbow is made from the refraction of light off of droplets of water or ice at a distance, two different people standing side by side won’t see exactly the same rainbow. They will each have a slightly different line of sight, so the light will be reflected by different water drops or ice crystals. Thus, each will see a different rainbow.
* If the atmospheric conditions are just right, a person might see a double rainbow; one rainbow above another. These are fairly rare and the outer rainbow is actually a mirrored reflection of the other. For this reason, the outer rainbow’s colors are in reverse order.
* Using the pneumonic Roy G Biv, the order of the colors of the rainbow can be remembered; Red, Orange, Yellow, Green, Blue, Indigo and Violet. This means that the order of the colors of the outer bow in a double rainbow can also be remembered, since they are in reverse order; Violet, Indigo, Blue, Green, Yellow, Orange and Red.
* One of the most fascinating things about rainbows is that what we see is usually just part of it, cut off by the horizon so it appears as a semi-circle. In actuality, a rainbow describes a perfect circle, which you’d see if there was no horizon. This has been proven from altitudes high enough, such as in low orbit, to see the curvature of the earth without the horizon getting in the way.
As a matter of fact, if conditions are right, we can occasionally see a halo or corona around the sun or moon. This is actually a full rainbow that we see as a halo. In the following picture, it is hard to see, but there is a full rainbow encircling the moon.
Rainbows are beautiful and fascinating. Double rainbows and halos are rarer, but even more stunning. I’ve been fortunate enough to see a double rainbow four times; once on the Oregon coast and three times here in the Montana Rockies.
Have you ever seen a double rainbow?
Mountain Man’s Affiliate store for great gifts and more
Posted in science and tagged double rainbow, facts, light refraction, moon halo, rainbow, sun halo, sunlight by rextrulove with 10 comments.