Re: Doppler question

[Leigh Palmer <palmer@sfu.ca>]

> I always thought motion was relative. Why is it if the source
> emits a 440 hz and it moves towards the observer at 30 m/s, the
> observer hears 482 hz.(c=345). But if the observer moves
> towards a 440 hz sound source at 30 m/s, the observer hears 478
> hz. Why are these two heard frequencies different? In both
> questions the observer and the source are approaching each
> other. What *conceptually* is going on here?

You have neglected motion of the medium. That is not a problem
with light; there is no medium. With sound there is a medium.
It was precisely this difference that led to the formulation
of the special theory of relativity (or SRT if you're left-
handed).

Leigh