Audience: Elementary and Middle School Students
A double-rainbow, with the second arc visible. Most rainbows have two arcs, but they are not always visible. Photo by pcess609 from Unsplash.
There are many myths surrounding the rainbow’s colored curve: the pot of gold gleaming, just waiting to be discovered at the end, and the leprechauns who dance around that sacred spot where the rainbow hits the grass. While these stories aren’t entirely true, a rainbow cannot be discounted in the realm of magic. The beauty of this phenomenon is nothing short of enchanting, as the storm and sun mingle to form a stretch of colors. A rainbow is the perfect culmination between science and nature, light reflections, water droplets, and the color spectrum.
First, how is a rainbow formed? Rainbows are created from sunlight dispersed through fog or raindrops, in the process of refraction. Refraction is when sunlight moves through one medium to another that is denser than air, switching directions with the reflection and refraction captured by the human eye as colors. This often occurs when the sun emerges after the rain has subsided, due to the high moisture content in the air. Rainbows usually last in their vibrance for an hour on average.
Furthermore, we know that color is formed when light refracts through rain droplets, but how does the human eye perceive color? Sunlight has a myriad of wavelengths that each correspond to a color on the color spectrum. This includes red, orange, yellow, green, blue, indigo, and violet, or the famous acronym ROYGBIV. The angle of the light refracting through the water droplet is also significant in the way we observe colors. This means that each viewer of a rainbow sees something different based on their angle and perception of the blurring hues. Furthermore, the observer must be positioned in the correct spot to even see the rainbow. The water droplets must be in front of the spectator with the sun behind them, and the arc of the rainbow must be below 42°.
There are numerous conditions that must be met to view a rainbow, but rainbows have never seemed like a very rare phenomenon. Most of us have caught glimpses of this colorful show in the sky multiple times throughout our lives. However, despite its common appearances after rainstorms, there are many things people don’t realize about rainbows. Rainbows are not half arcs, but actually full circles. However, from our angle, we can’t see the other half of the rainbow’s multi-hued arc. The rest of the circle is only visible from certain points in the sky. Rainbows also always exist as double-rainbows. Double rainbows are two rainbows seemingly stacked on top of the other, light twice-reflected in a single drop of water. Depending on your view, you might see a more washed-out second curve, or none at all. It is completely contingent on one’s perspective of the rainbow. Furthermore, rainbows are an optical illusion. You cannot ever reach the end of a rainbow, not because rainbows magically move, but because it is simply impossible. Our view of a rainbow changes depending on where we are, constantly-shifting, so unfortunately, we will be forever unable to reach the fabled pot of gold at the end.
Next time you look at a rainbow, know that it’s much more than the colorful object of stories. Instead, it’s a manifestation of science in its most beautiful form, a gift to the viewer. Rainbows aren’t all that meets the eye. Whether it’s a hidden complete curve, or an unseen double arc, rainbows are one of Earth’s most gorgeous wonders. While the magic from storybooks and fairytales aren’t accurate when applied to rainbows, nature’s perfected recipe of water and sunlight into this startling phenomenon is something enchanting in itself.
Bibliography:
Evers, Jeanie, Rainbows, National Geographic, https://education.nationalgeographic.org/resource/rainbow/
Wells, Sarah, The Science behind Rainbows, Smithsonian, The Science Behind rainbows, https://ssec.si.edu/stemvisions-blog/science-rainbows
Henderson, Austin, How Stuff Works? How do Rainbows Work?, https://science.howstuffworks.com/nature/climate-weather/atmospheric/question41.htm
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