Gravitational red shift question

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  • #1
asdf1
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Why does the frequency of a photon emitted from the surface of a star decrease as it moves away from the star?
if hf`=hf(1-GM/(R*c^2)
then as the distance becomes larger, R becomes larger, so f`becomes smaller?
 

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  • #2
TD
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We use the fact that the total energy must remain constant.
I'm not 100% sure, but I think t hat when leaving the star, the photon has to get out of the gravitation-field of the star, therefore its kinetic energy has to decrease since the potential energy is rising.
 
  • #3
asdf1
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hmm... that makes sense, but the mathematical equation looks weird...
it seems to say otherwise~
 
  • #4
asdf1
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still a little weird~
 

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