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

Homework Help: Phase and Group Velocity Problem

  1. Nov 20, 2011 #1
    1. The problem statement, all variables and given/known data


    http://www.flickr.com/photos/55153239@N03/6371848305/ [Broken]

    2. Relevant equations

    vp = w/k

    vg = dw/dk

    3. The attempt at a solution

    I know the relationship of:

    vg = vp(1+lambda/n * (dn/dlambda))

    but i don't know where to go from here..
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Nov 21, 2011 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    1. given n(λ), what is phase velocity vp of light of wavelength λ?
    2. as you state, w/k = vp. So how about rewriting w in terms of λ and n(λ), using (1) above?
    3. use chain rule dw/dk = dw/dλ*dλ/dk
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook