Why is the sky red at sunset and sunrise ?
Premise
This article builds upon the last one I wrote:
I have linked it here for you to read if you want to delve into the topic of the colors of the sky and why they change. Furthermore if you don’t understand something in this story, it is probable you will find the answer in my previous article.
Sunset and sunrise
At sunset and sunrise the sun is low in the sky, which means that the light we see travels through much more atmosphere. This longer path gives the opportunity to light to be scattered more.
With enough scattering, almost all the shorter wave lengths (green, blue and violet) can be removed. Thus only the longer wavelengths (red, orange and yellow) remain in the beam of light. As the sun gets lower in the sky the predominant color will become red since it has the longest wavelength and doesn’t get scattered by the air molecules.
Since the light at sunset or sunrise is orange/red, also the clouds in the sky will appear orange/red.
Clouds
Since we talked about clouds, let’s see what happens when the light hits a cloud and why they appear white/grey.
When light strikes a cloud, white light is reflected. This happens because clouds are aerosols consisting of a visible mass of miniature liquid droplets and frozen crystals which are much larger than air molecules. Because of this they scatter all the wavelengths more or less equally. Since almost all the light that hits a cloud will be scattered and all the wavelengths are scattered, clouds appear to be white.
Particulates
Particles are much bigger than air molecules, but smaller than ice crystals and droplets. However they scatter light in the same way as the latter. The light scattered from particulates is, indeed, white since they are bigger than all the wavelengths of light.
I hope you found the article interesting. Feel free to leave a feedback.
