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B Doppler Effect In Radio Waves

  1. Feb 6, 2017 #1
    I have learned that the Doppler effect causes a change in wavelength (and thus frequency) in all types of waves
    Suppose there is a radio station transmitting waves of frequency 90 kHz and the antennae in my car is tuned to that frequency.
    Then I start to accelerate and thus I am changing my position relative to the station .
    Then due to Doppler effect the waves would have to travel a longer distance and thus there has to be a change in frequency of the waves due to energy loss.
    But I can still hear the radio at that frequency , why does this happen?
  2. jcsd
  3. Feb 6, 2017 #2


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    [edit] Hello shihab, :welcome: !

    This happens because your radio may be tuned to 90 kHz exactly , but it also perfectly receives the 90000.009 HZ the antenna picks up when you are driving towards the sender at 108 km/h, or the 89999.991 Hz when you drive away from it.

    In short: because your speed / wave propagation speed is so small (like 30/300000000 in this example)
  4. Feb 6, 2017 #3
    So you mean to say that
    So, you mean to say that as my speed or velocity is very small compared to that of the radio waves that is why the frequency does not change by a huge amount ?
    Is the loss in energy small?
  5. Feb 6, 2017 #4


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    Correct. 0.009 Hz really is a very small amount :smile: of shift for a radio wave.
    What loss in energy ?
  6. Feb 6, 2017 #5
    Okay, I now understand .
    Thank You.:smile:
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