Atmospheric optics deals with how the unique optical properties of the
Earth's atmosphere cause a wide range of spectacular
optical phenomena. The blue color of the
sky is a direct result of
Rayleigh scattering which redirects higher
frequency (
blue)
sunlight back into the field of view of the
observer. Because blue light is
scattered more easily than red light, the
sun takes on a reddish hue when it is observed through a thick atmosphere, as during a
sunrise or
sunset. Additional particulate matter in the sky can scatter different
colors at different angles creating colorful glowing skies at dusk and dawn. Scattering off of
ice crystals and other particles in the atmosphere are responsible for
halos,
afterglows,
coronas,
rays of sunlight, and sun dogs. The variation in these kinds of phenomena is due to different particle sizes and geometries.