# Question about Doppler effect

1. Mar 13, 2005

### Raparicio

Hello.

I have a question on Doppler effect. When the wave has the same velocity that the emisor, u have this:

$$f= \frac {\partial {(Vs-Vo)}} {\partial {(Vs-Ve)}} f'$$

In this case, Vs=Ve, f=infinite???

2. Mar 13, 2005

### Timbuqtu

Theoretically, yes. When the emitter travels at the speed of sound, the emitted waves travel along with the emitter and therefore the wavelength will go to zero. So f = Vs/wavelength goes to infinity. That's why you here a blast when a jet reaches sound speed.

3. Mar 13, 2005

### Raparicio

d

Where can i find the demonstration of doppler formula???

4. Mar 13, 2005

### dextercioby

There's an elegant proof for the Doppler-Fizeau formula in electrodynamics books.I'm sure that setting "c"----"v_{sound}" & making approximations u can find the nonrelativistic cases...All 4 of them (in the case of leght,there are only 2).

Daniel.

5. Mar 13, 2005

### Raparicio

Dear Dextercious:

Setting where???

6. Mar 13, 2005

### dextercioby

In the general Doppler-Fizeau formula...

Daniel.