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Homework Help: Finding the speed of quaser using the Doppler equation

  1. Oct 20, 2012 #1
    1. The problem statement, all variables and given/known data
    The Hβ line of the hydrogen atom's spectrum has a normal wavelength λβ= 486 nm. This same line is observed in the spectrum of a distant quasar, but lengthened by 19.0nm . What is the speed of the quasar relative to Earth, assuming it is moving along our line of sight?

    2. Relevant equations

    f' = f(1 + u/c)

    3. The attempt at a solution

    I converted the wavelengths into frequencies to solve for u and got 6.17e14 Hz = 5.94e14 Hz(1+ u/3e8m/s)). Then I solve for u and keep getting 1.17e7 m/s, which is incorrect. What am I doing wrong?
  2. jcsd
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