Dopplershift, using changing optical length

[Anton Alice]

Hello,

again a simple question:

consider a mirror, with a transparent layer (index of refraction n) of certain thickness on it.
If a ray is reflected by the mirror, while the mirror is moved normal to the plane, then one could observe a dopplershift.
But what happens if the mirror is fixed, while the thickness of the transparent layer changes with time?
I would equivalently expect a dopplershift, since the optical path length changes. But it's a little difficult to imagine, how the reflected wave form gets stretched/contracted.

 

[Buzz Bloom]

I would equivalently expect a dopplershift, since the optical path length changes.

Hi Alice:

I am thinking of a slightly different configuration. Suppose the stationary mirror is instead a source of pulses at a certain rate. Would you expect the pulse rate, or equivalently the length of time between pulses as seen by the observer, to change as the path length changes?

Hope this helps.

Regards,
Buzz