But isn't terminal velocity only relevant when there is a normal force of air? There isn't a terminal velocity for an object in a vacuum, except maybe C.
I thought that was implied, but I suppose I could have specified.
Also, it's not restricted to air. Terminal velocity is applicable to any momentous object present in a frame of reference with objects of different momenta (for example: water). It's less practical and far less predictable when in an area without an equally distributed substance, but it's still there.
C != c
. I'm not sure what C is, but the universal symbol for the speed of light is c (case does make a difference--E = energy, e = lim[n->infinity](1+1/n)^n). Terminal velocity is the maximum velocity an object can reach when under a constant acceleration due to frictional forces. Light does not undergo friction. Light slows down in particular mediums for other reasons. When a photon "collides" with an atom, an electron absorbs its energy and jumps to a higher energy shell. It very shortly moves to its original shell and re-radiates the energy. This reaction does not occur instantaneously, so as one might intuitively conclude, the more atoms that light "bumps" into on its path, the longer it takes.
The properties of refraction of light are also pretty interesting:
sin(angle1)/c1 = sin(angle2)/c2
With that relationship, you can measure the speed of light in various mediums.
Edit: Remembered. C is Coulombs, the SI measurement of charge.