Doppler effect, why is there a different equation when the source is moving and when the observer is moving?

Doppler effect, why is there a different equation when the source is moving and when the observer is moving. For sound, how does going faster than mach 1 affect the results? For light, what would be the red objects going the speed of light?

What would be the blue shift for objects going the speed of light? Asked by DMNHJP 32 months ago Similar questions: doppler effect equation source moving observer Science > Physics.

Similar questions: doppler effect equation source moving observer.

The equations are the same. The only thing that matters is the difference in speeds. If which end was "moving" was significant that would violate relativity, among other things.

If the source is exceeding Mach 1, then the equation is inapplicable, as it assumes the wave takes a straight path between the two points. If the source is moving at the speed of light, the trailing light will be infinitely red-shifted down to zero frequency and zero energy. The leading light will be blue-shifted to twice its normal frequency.

1 I hate physics. This user has been banned from Askville.

2 If that's your homework, I think you should have started Saturday morning! .

If that's your homework, I think you should have started Saturday morning!

3 That's actually incorrect, it does depend on whether the observer or the source is moving. The equation for a Doppler frequency shift (non-relativistic) is f'=f(v+v_o)/(v-v_s) for the motion towards each other, and switched signs for moving away from one another. It took me awhile to understand why it is dependent on which object is moving.

If the source is moving the wavelength changes. If the observer is moving the wavelength is the same, but the time between wavelengths is different.

That's actually incorrect, it does depend on whether the observer or the source is moving. The equation for a Doppler frequency shift (non-relativistic) is f'=f(v+v_o)/(v-v_s) for the motion towards each other, and switched signs for moving away from one another. It took me awhile to understand why it is dependent on which object is moving.

If the source is moving the wavelength changes. If the observer is moving the wavelength is the same, but the time between wavelengths is different.

4 Yep, you're right, the wavelength in the media changes if the source is moving, and it obviously does not when it's the observer who is moving. BUT in the end it makes no difference-- what matters from the observers point of view is the difference in speed between the two. For example I can talk to someone sitting one row ahead of me on a jet plane and they don't sound real funny, no matter what the speed.

But to a listener on the ground we'd sound like chipmunks as we're approaching.

Yep, you're right, the wavelength in the media changes if the source is moving, and it obviously does not when it's the observer who is moving. BUT in the end it makes no difference-- what matters from the observers point of view is the difference in speed between the two. For example I can talk to someone sitting one row ahead of me on a jet plane and they don't sound real funny, no matter what the speed.

But to a listener on the ground we'd sound like chipmunks as we're approaching.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.