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Doppler effect problem

  • Thread starter Benzoate
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Homework Statement



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.

Homework 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))


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
 

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