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Why are things blue shifted and not violet shifted?

  1. Oct 26, 2009 #1


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    Gold Member

    If objects are moving away from us, they are known as red shifted, so why are objects moving towards us blue shifted and not violet shifted?
  2. jcsd
  3. Oct 26, 2009 #2
    Semantics. Blue-shifted objects are not necessarily blue: an object emitting at 5 um moving towards us is still blue shifted even though it is way outside the visible spectrum.
  4. Oct 26, 2009 #3


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    Science Advisor

    "blue" and "red" are just labels used to denote upshift or downshift in frequency.
  5. Oct 26, 2009 #4


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    Gold Member

    Oh ok, yeah I just thought it was odd since most elemtary school students even know that purple comes after blue using roygbiv. Thanks :]
  6. Oct 28, 2009 #5
    I didn't know that.

    So acceleration of the object in relation to us alter wave length?

  7. Oct 28, 2009 #6


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    Homework Helper

    What? Entropee said nothing of the kind.
  8. Oct 29, 2009 #7


    Staff: Mentor

    Actually, purple is not the same as violet. Violet is a spectral color consisting of wavelengths shorter than blue, but purple is a perceptual color seen only when both blue and red wavelengths are present.
  9. Oct 29, 2009 #8


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    Oh lol, my bad, I guess it's time for me to go back to Elementary school?
  10. Oct 29, 2009 #9
    But what he said is right?

    I wanna know why!

    Edit: Ok so I guess I just got pretty inventive with lack of clear information. LOL
    Last edited: Oct 29, 2009
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