Air resistance, the friction between air an objects moving through it,
has no effect on light. However, light does travel just a bit slower in
air than in a vacuum. That's because the air, like any other material,
has charged particles in it which oscillate along with the light wave's
electrical fields, slightly changing the way the light propagates
through.
Air resistance gradually drains the kinetic energy of something
travelling through air, turning it into heat. The closest thing to that
for light in air would be the very weak absorption of light by air,
which gradually turns the light energy into heat. Obviously visible
light can go a very long way in clean air before much of that happens,
since air is nearly transparent.
Mike W.
(published on 10/22/2007)
