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

Derivation of group velocity.

  1. Sep 10, 2013 #1
    I was reading the derivation on Wikipedia:

    http://en.wikipedia.org/wiki/Group_velocity#Derivation

    Why is the first part before the integral sign ignored when calculating the velocity? Surely it would also cause a phase shift in some time interval and make the waves move forward (or backward)?
     
  2. jcsd
  3. Sep 10, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Group velocity cares about the speed of the amplitude, phases are not relevant for the group velocity.
     
  4. Sep 11, 2013 #3
    Ok, but when calculating the velocity by dividing the terms in front of t by those in front of k, why can some of the terms in front of t be ignored?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Derivation of group velocity.
Loading...