1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Does a spherical wavefront thicken as it moves outwards ?

  1. Jul 14, 2012 #1
    If a flash of light is emitted spherically and this is measured in terms of its duration by two distant observers with one twice as far away from the source as the other, and the source and observers are all at rest with respect to each other, will the flash appear to have the same duration for both observers.
  2. jcsd
  3. Jul 14, 2012 #2


    User Avatar
    2017 Award

    Staff: Mentor

    It depends on the shape of the flash and the medium the light is in. In vacuum, there is no change at all.

    In most setups with a medium (for example, air), I would not expect any significant change
    For very short pulses, the distant observer might record a longer pulse.
    If you prepare the pulse in the correct way, the distant observer can observe a shorter pulse.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook