Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why the frequency in both shallower and deeper part is the same?

  1. Mar 28, 2005 #1


    User Avatar

    Use water waves as examples.
    Put something in the water. When you produce a wave, refraction will occur on above the 'something'.
    But why the frequency in both shallower and deeper part is the same?
    In addition, the wavelength in the shallower part reduce. Does this means the engery of the wave increase?
    Last edited: Mar 28, 2005
  2. jcsd
  3. Mar 28, 2005 #2

    Claude Bile

    User Avatar
    Science Advisor

    The energy of the photons that comprise the wave is proportional to their frequency. If there were a frequency change at an interface, this would mean energy is being gained or lost at the boundary. Since this is not observed to happen, we conclude that the frequency does not change.

    A more quantitative reason is imposed by Maxwell's equations. Maxwell's equations in optical media demand that the electric field be continuous over the boundary for all time. This is only possible if the frequency of the wave does not change.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook