[Boot Hill]

richtig_faust says:   "Except for the fact that color is based on FREUQUENCY not momentum ..."

Your statement is incorrect. Frequency is intimately connected to the photon's momemtum because when a photon looses momentum, the result is a loss of energy. And the consequence of a photon losing energy, is a decrease in frequency, i.e., a red shift. See below.

momentum:
p = m*v

energy of a photon:
E = h*f = mc²
      (where h = Planck's constant)

and by combining eq. 1 and eq. 2, we get the momemtum of a photon:
p = h*f/c
      (where c = speed of light)

From eq. 3 it can be seen that if the photon's momentum (p) decreases, the frequency (f) must also decrease.

--Boot Hill

[richtig_faust]

You are making that assumption based upon the particle nature which is indeed related to plank's constant (but you forgot the divisor of 2*pi). BUT doppler shift is a frequency shift measurement, they are NOT measuring momentum, they measure FREQUENCY.


A good example of equipment that indirectly measures angular momentum is a Magnetic Resonance Imaging machine which catches frequency shift based upon the change in angular precession.