Ok, so we all know why the sky is blue, right? And, some may even be familiar with a common physics demonstration where a white light is shone through a milky substance which appears blue when viewed from the sides due to light scattering, specifically Tyndall scattering. So, if the sky is blue from scattering, then why should we find blue in the rainbow?
I WAG the blue in the rainbow is residual from inefficiencies in scattering?
Blue is in the rainbow because it’s a color – an intrinsic color, a wavelength of light. It has nothing to do with the atmosphere. If you were in the vacuum of space, and projected sunlight through a prism, you’d see the same familiar spectrum of colors, including blue, in the same spot, next to Roy G and Iv.
The sky is blue because blue light scatters more widely than red light does. Why the sky isn’t indigo or violet…um…I dunno. They have even shorter wavelengths, and should scatter even more widely, shouldn’t they?
Most blue sunlight isn’t scattered. The part that isn’t gives the blue part of the rainbow.