Rainbows: The Atmosphere’s Dance Of Color

| August 26, 2019 @ 2:30 pm


(Credit: NCAR, NWS)
In a world full of vibrant color, nothing quite vanquishes the atmospheric phenomenon that is the rainbow. Everyone has awaited the arrival of a rainbow once rainfall has ceased. Almost always, the ever reliable rainbow traverses across the sky emitting light in all wavelengths thus presenting its renowned look. But what does it take for these bows of color to form?
Rainbows are meteorological phenomenon that are caused by the reflection, refraction and dispersion of light in water droplets. This results in a spectrum of light appearing in a bow-like structure in the skies above. When observing a rainbow, one will notice that the outer part of the arc is red and the inner part is violet. This is caused by light being refracted when it enters a droplet of water, then reflected on the back side of the droplet and refracted again before leaving the water droplet. The rainbow effect occurs due to incoming light being reflected back over an angle range of 0 degrees and 42 degrees, with most intense light at 42 degrees. The reason the returning light is most intense at 42 degrees is because 42 degrees is known as the turning point—light hitting the outermost ring of the droplet and returning to the center at less than 42 degrees.
The amount of light that is being refracted is dependent on its wavelength, and hence its color. This is referred to as dispersion. Blue light, which has a shorter wavelength, is refracted at a greater angle than red light. But, due to the reflection of light rays from the back of the water droplet, blue light emerges from the droplet at a smaller angle. This causes blue light to appear on the inside of the rainbow arc and red on the outside of the rainbow arc. 

Rainbows do not exist at one particular location either. In fact, many rainbows can exist, but only one can be observed depending on the observer’s viewpoint. All raindrops reflect and refract sunlight in similar ways, but only some light from raindrops reaches the observer’s eye. Rainbows appear to be curved due to the angle between the observer, the water droplet, and the sun. This angle perfectly creates the rainbow phenomenon between 40 and 42 degrees to the line between the observer’s head and their shadow.

Rainbows can be observed all around the globe and present a tranquil end to rainfall. Truly, rainbows are awe-inspiring enough that Pink Floyd depicted the dispersion effect on their The Dark Side of The Moon album. Everyone enjoys a rainbow that traverses across the sky and presents its dance of color, so be sure to look out and around when rain has ceased to fall to observe the atmosphere’s true color.

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©2019 Weather Forecaster Alec Kownacki

AlabamaWX is pleased to partner with the Global Weather and Climate Center team for outstanding posts about our atmosphere. Visit them at https://www.globalweatherclimatecenter.com for more great information!


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