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Doppler effect of light source

  1. Apr 12, 2012 #1
    A source and a receiver is at rest with each other. Source emits some couple of light pulses, and stops emitting more.

    1. The pulses is not reached to the receiver yet, and source starts moving. Does the receiver experience doppler effect with the emitted pulses?

    2. The pulses is not reached to the receiver yet, and receiver starts moving. Does the receiver experience doppler effect with the emitted pulses?

    Thanks.
     
  2. jcsd
  3. Apr 12, 2012 #2

    jtbell

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    Staff: Mentor

    The answer to both questions is "no." After the pulses have left the source, their propagation (relative to a receiver, or indeed relative to any inertial reference frame) is not affected by later changes in the motion of the source.

    The same applies to baseballs, or cricket balls if you prefer. :smile:
     
  4. Apr 12, 2012 #3

    ghwellsjr

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    Gold Member

    No.
    Yes, if he moves toward or away from the source. If he moves at a right angle so his distance from the original location of the source remains constant, then no. EDIT: actually, it is more complicated than this as he has to take a specific path for there to be no Doppler.
     
    Last edited: Apr 12, 2012
  5. Apr 12, 2012 #4
    Thanks ghwellsjr.
     
  6. Apr 12, 2012 #5

    jtbell

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    Staff: Mentor

    I'm sorry, I misread the second question, because the two are so similar. The answer to that question is "yes." However, the amount of doppler shift perceived by the receiver does not depend on whether the source has changed its motion after emitting the pulses; this is what my original "no" was intended to convey, which does not answer the question that was actually asked.
     
  7. Apr 12, 2012 #6
    That's ok, jtbell. Thanks.
     
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