The removal of the shorter wavelengths of light is due to Rayleigh scattering by air molecules and particles much smaller than the wavelength of visible light (less than 50 nm in diameter).The scattering by cloud droplets and other particles with diameters comparable to or larger than the sunlight's wavelengths (> 600 nm) is due to Mie scattering and is not strongly wavelength-dependent. Mie scattering is responsible for the light scattered by clouds, and also for the daytime halo of white light around the sun (forward scattering of white light). Without Mie scattering at sunset and sunrise, the sky along the horizon has only a dull reddish appearance, while the rest of the sky remains mostly blue and sometimes green.
