The Doppler effect for light (or other EM wave) is actually simpler than the Doppler effect for sound because for light it is simply a relative velocity phenomenon.

f / = f

(

1 ±

u c

)

where u is the relative velocity between the source and observer. Use the plus sign for relative motion toward and the minus sign for relative motion away.

Often what matters is the shift in frequency. This is:

f / - f = ±

u f c