Is there an effective way to use the doppler effect?

Question

jamesj · Answer

A useful way you mean?  Yes.  The doppler effect works with all waves, not just sound.

So it works with light waves as well.  Doppler shift of light makes it more red if the object is moving away from us and bluer if it is moving closer.

Red shift is a major tool in astronomy and astrophysics to determine how fast distant astronomical objects such as galaxies are moving relative to us.

anonymous · Answer

Is that why some starts look orange or red?

jamesj · Answer

No.  They appear different colors to our eye normally because they are at a different life stage or have a different chemical composition from our sun.  Our sun will in a few billion years become a red giant, red because it will be burning at a lower temperature.

It's a nice fact that our vision evolved so that the center of our optical range actually matches the center of the spectrum of the sun.

jamesj · Answer

You might like this: http://www.universetoday.com/24640/color-of-stars/

anonymous · Answer

Thanks!

anonymous · Answer

Thats a really cool subject, im gonna have to read more about it.

jamesj · Answer

Nice.  Look up "red shift" then.

anonymous · Answer

What is red shift?

jamesj · Answer

"red shift" is the standard term for the first effect I described to you, where the frequency light of distant galaxies is changed due to the Doppler effect.

jamesj · Answer

http://en.wikipedia.org/wiki/Redshift

anonymous · Answer

Oh, cool

anonymous · Answer

But this says that it IS associated with the doppler effect, just like this http://en.wikipedia.org/wiki/Doppler_effect look under astronomy

jamesj · Answer

Yes, that's what I'm saying.  I'm saying that the doppler effect applied to light waves leads to red (and blue) shift.  So it is an application of Doppler theory.

anonymous · Answer

But that still doesnt answer my original question, what is an useful use for it?

jamesj · Answer

You'll find lots of applications in the wikipedia article: http://en.wikipedia.org/wiki/Doppler_effect#Application

anonymous · Answer

Oh! So its pretty much used as a way of telling people that something with a siren is getting nearer?

jamesj · Answer

For example.  But even more pragmatically with radar, or medical applications.  Anyway, you can read all about it.

I happen to think the astronomy application is the most impressive, as we're using it to understand the structure of our entire universe.

anonymous · Answer

I absolutely agree with the astronomy application being the most impressive. It is by far the most interesting and exciting.

Probably the most typical answer though, and commonly-encountered situation, would be radar guns, used by police and for a variety of other purposes to determine the speed of an object, by relying on the Doppler effect to determine the change in frequency of the signal returned from the object in question. I'm not entirely sure if the most modern of such equipment relies entirely on this or if there are other methods involved, but it's certainly their origins. I'm sure you're already aware of this though ;)