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Why, when there is a rainbow, is there typically only one? Following or during a rainstorm, why isn't the sky full of rainbows rather than just the one that we see?
I hope you understand the question. Last night we were driving home and our five-year old saw a rainbow and we wondered if the moisture and sunlight are just right to produce one rainbow, why doesn't it produce numerous rainbows?
Thanks! John P.
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Your son is already looking for weather phenomena, perhaps he has a bright future in the field! Rainbows are one of mother natures truly beautiful optical effects. First we must understand how rainbows are formed, and then we can figure out why there aren't rainbows every time it rains outside.
You need to have the sun at your back to see a rainbow. So at lunch time when the sun is overhead and even though it might be raining around you, you aren't going to see a rainbow then. Often time we see them in the later afternoon or evening when the sun is behind you or at at lower angle, and sometimes in the early morning.
Light is bent (refracted) inside the raindrops that are falling. This causes different wavelengths or colors of light to separate. Only one color of light can be observed from each drop, so you need a whole ton of raindrops to see the rainbow.
If you think about when it's raining all day, a lot of the time it's totally overcast, so without that sun behind you, you won't see anything but rain. In the spring, summer and fall though, you can get thunderstorm or patchy rain and patches of sun, so be on the look out for rainbows.
The sky isn't full of rainbows everywhere because the sun has to enter the raindrop at specific angle to create the bow. This means the raindrops need to be in the right place at the right time with the sun at the specific angle. Also of note, each person sees their very own rainbow since we stand in different places!
The link on the right is one of the neatest rainbow pages I've seen probably ever, it's interactive and you can click on the pictures to figure out what's in the sky.
Answered by KSL Meteorologist Dina Freedman
