orange/red sunsets in a clean atmosphere

  • created by rayleigh scattering
  • at mid day, only a bit of the short wavelengths of visible light are scattered since the radiation is passing through a small distance in the atmosphere.
  • at sunset, however, the radiation must pass through a much thicker layer of the atmosphere
  • when the sun is at an angle of 4 from horizontal, the atmosphere appears to be 12 times thicker than at midday
  • hence, much more blue light, and some green light are scattered
  • therefore, the sun appears to look orange/red.
  • this is for the case when the atmosphere is relatively clean, how will a sunset look when it is polluted?????