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Homework Help: Doppler effect problem

  1. Aug 13, 2007 #1
    1. The problem statement, all variables and given/known data

    A distant galaxy moving away from us at speed 1.85 *10^7 m/s. Calculate the fractional redshift (lambda'-lambda(0))/(lambda(0)) of the light from this galaxy.

    2. Relevant equations
    (lambda'-lambda(0))/(lambda(0))=lambda'/lambda(0)-1;
    f=(sqrt(1-beta)/sqrt(1+beta))*f(0)
    f/f(0)=lambda/(lambda(0))


    3. The attempt at a solution

    lambda(0))/lambda=f/f(0)= sqrt((1-beta)/(1+beta))=.980 since the galaxy is receding.

    (lambda-lambda(0))/lambda(0)=(lambda/lambda(0))-1

    1/(f/f(0)) = lambda/(lambda(0))=1.0204

    therefore the fractional redshift is :

    (lambda-lambda(0))/(lambda(0)=(lambda/lambda(0))-1= 1.0204-1=.0204
     
  2. jcsd
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