[Phys-L] Re: relativistic doppler effect (was: The view from the Enterprise.)

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

----- Original Message -----
From: "John Mallinckrodt" <ajm@CSUPOMONA.EDU>


> Let's take this specific example and just run some numbers.  Suppose
> the rest frequency is 2 Hz so that, at v = (3/4)^1/2 c it becomes 1
> Hz.  The source emits a pulse and one second later (according to the
> observer "at rest") it emits another pulse.  In that one second the
> source moves (3/4)^(1/2) of a light second while the first pulse
> moves a full light second.  The pulses are, thus, 1 - (3/4)^(1/2) of
> a light second apart.  This is the wavelength and it corresponds to
> an observed frequency of
>
>    f_obs = [1 - (3/4)^(1/2)]^-1 Hz = 7.46 Hz
>
> in agreement with the general formula.
But now adding the Lorentz contraction lowers this to 3.75 Hz according to
the relativistic Doppler effect.  I'm not sure to what frame I apply the
contraction here to get that result rather than twice John's answer.
Someone want to explain?

Rick
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