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Homework Help: How Do I Solve These Problems?

  1. Oct 17, 2012 #1
    I've memorized all the formulas I need for my first intro to physics class...But I am still trying to get familiar with what formula to use for what problem. Here are two questions. If someone could tell me what formula i would use to solve them, that would be great!!

    1. At what rate does a protostar with a temperature of 2500k radiate most strongly?

    (I'm thinking that we would want to use weins laws that states lambda max is equal to 1/temp. But 1/2500k does not give me a wavelength....)

    2. In a far away galaxy, light is emitted with an average wavelength of 450nm. If this galaxy is moving away from earth at a rate of 1.3*E8 m/s, what wavelength of light will we see?

    (So if its moving away that tells us that it will be a redshift...But how do we get the exact wavelength? I'm thinking that we would divide the recessional velocity of 1.3*E8 by our constant 3*E8, which would give us 2.31m. And then we would say that our

    change in wavelnth/true wavelenght of 450 = to 2.31 m/s

    Am I on the right track here? This gives me 1038, but I'm guessing I need to convert one of these two first. Or maybe I'm doing this completely wrong....)

    P.S.-You people have been awesome with your previous help. I hope that one day I am able to answer peoples questions!
  2. jcsd
  3. Oct 17, 2012 #2
    It may be just me, but the question is meaningless. One could ask just at what rate a protostar with a given temperature radiates, but "most strongly" makes this incomprehensible.

    What is the Doppler shift formula?
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