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# Doppler Effect--->clarification needed! watch

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1. Can someone fully explain the doppler effect to me...glad nothing on it came in PHY4 ...might pop in on Monay, thats why need your help!
2. When something is moving away from you, and it emits radiation, the wavelength of the radiation is "streched". So you get red shifts from stars moving away, and blue shifts from stars coming towards us (very rare... I don't know if this exists). I don't know exactly why.

You also get gravitational red-shifting, where radiation is emitted against the direction of a gravitational field, but this is more confusing so I'll leave it to someone else to explain properly..
3. If a wave source is moving towards the observer, each wave crest will have less distance to travel so the wavelength will appear shorter than it actually is (blue shift for light). If the source is moving away, the opposite happens.
4. (Original post by mik1a)
blue shifts from stars coming towards us (very rare... I don't know if this exists).
I think it happens in a binary, or more, star system.
5. (Original post by IntegralAnomaly)
I think it happens in a binary, or more, star system.
Would that be noticable? I thought it was to tell the average ratio of velocity from a point to the distance (indicating faster stars are further from the centre, supporting the big bang), so the mere orbit of a star would be insignificant to the star's actual velocity through space. Although I could be wrong, and no matter how small I can't argue that there would be some contraction in wavelength when the star is travelling "towards" the Earth in its orbit.
6. The Andromeda galaxy shows blue shift I think
7. (Original post by mik1a)
Would that be noticable? I thought it was to tell the average ratio of velocity from a point to the distance (indicating faster stars are further from the centre, supporting the big bang), so the mere orbit of a star would be insignificant to the star's actual velocity through space. Although I could be wrong, and no matter how small I can't argue that there would be some contraction in wavelength when the star is travelling "towards" the Earth in its orbit.
But what about a star in a binary that is quite close to earth(hence slow recession velocity) and also has a quite high angular speed?Then i think the blue shift would be quite significant.
8. Thanks a bunch all of you....really cleared my mind....cheers

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