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Homework Help: Spectral line

  1. Oct 25, 2007 #1
    1. The problem statement, all variables and given/known data
    One of the most prominent spectral lines of hydrogen is [tex]H_\alpha[/tex] line.A bright red light with wavelength of [tex]656.1\times 10^{-9}m[/tex].What's the expected wavelength of the [tex]H_\alpha[/tex] line from a star receding with a speed of 3000 km/s?

    3. The attempt at a solution

    Is it just [tex]\lambda=\lambda_o-\frac{\lambda_ov}{c}[/tex]
  2. jcsd
  3. Oct 25, 2007 #2
    I believe that should be: [tex]\lambda=\lambda_o+\frac{\lambda_ov}{c}[/tex]

    When objects move away from the observer, the doppler shift, increases the wavelength (red-shifts it).

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