A HeNe laser produces light with a wavelength of 632.8nm. The neon atoms, which emit the light, are moving at a mean velocity of 406m/s?

a. What is the difference in the observed freq of light emitted from Ne atoms moving direction toward the exit mirror as opposed to those which are moving away from
the exit mirror?

b. If the cavity length is 40cm how many cavity modes will be observed in the output
spectrum? Use the freq calculated in a) as the width of the output spectral line).