Compare and contrast Rayleigh scattering, Mie scattering, and nonselective scattering, and then explain why the sky is blue, sunsets are red, and clouds are gray

Question

What will be an ideal response?

Answer 1

Answer: Rayleigh scattering is performed by individual gas molecules in the atmosphere. It primarily affects shorter wavelengths. Rayleigh scattering is particularly effective for visible light, especially those colors with the shortest wavelengths, so blue light is more effectively scattered by air molecules than is longer-wavelength red light. Microscopic aerosol particles are considerably larger than air molecules and scatter sunlight by a process known as Mie scattering. Unlike Rayleigh scattering, Mie scattering is predominantly forward, diverting relatively little energy backward to space. Furthermore, Mie scattering does not have nearly the tendency to scatter shorter-wavelength radiation that Rayleigh scattering does. Thus, on hazy or polluted days (when there are high concentrations of aerosols) the sky appears gray, because the whole range of the visible part of the spectrum is effectively scattered toward the surface. Clouds reflect all wavelengths of incoming radiation about equally, which is why they appear white or gray. Because of the absence of preference for any particular wavelength, scattering by clouds is sometimes called nonselective scattering. The scattering of shorter wavelengths enhances the redness of sunrises and sunsets during episodes of heavy particulate concentrations.