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B How to calculate the Doppler Shift Frequency

  1. May 30, 2017 #1
    I would like to know the formula for calculating the Doppler shifted frequency received by someone on Earth that is received from a space ship traveling at 85 percent the speed of light away from Earth. Please show example of the formula being used. Lets say the spacecraft sent a radio signal from the ship at 100 MHZ what would the received frequency of that signal be on earth?
     
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  3. May 30, 2017 #2

    PeroK

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    Have you tried googling for "relativistic Doppler shift"?
     
  4. May 30, 2017 #3
    Yes I have looked but I would like to see someone actually do it with real numbers and a bit of explanation I am curious as to how the time dilation works in the scheme of things. In other words what would it look like if I were in a space ship traveling at 99% the speed of light towards a group of stars. Would the light of the stars be blue shifted? If so, by how much?
     
    Last edited: May 30, 2017
  5. May 30, 2017 #4

    PeroK

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    The equation is:

    ##f_o = f_s \sqrt{\frac{1+v}{1-v}}##

    Where ##f_o=## is the observed frequency, ##f_s## the frequency of the source and ##v## is the speed expressed as a fraction of the speed of light. E.g. ##v = -0.85## or ##v = 0.99## in the two examples you wanted. If ##v## is positive then motion of the source is towards the observer and if ##v## is negative then motion of the source is away from the observer.

    You could put that formula into a calculator or spreadsheet and plug away!
     
  6. May 30, 2017 #5
    Oh Man, Thanks this is perfect thanks so much! This is exactly what I was looking for! Going to have fun putting this is to a program and trying different values.
     
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