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!

Estimate the mean free path of phonons in Germanium at 300K using the following data

  1. Feb 14, 2012 #1
    1. The problem statement, all variables and given/known data

    If all the heat transport is by phonons, estimate the mean free path of phonons in Germanium at 300K using the following data. Thermal conductivity=80W/K m; Debye temperature=380K; atomic weight=72.6; sound velocity=4500m/s; density=5500kg m[itex]^{-3}[/itex]

    2. Relevant equations

    K=C[itex]_{V}[/itex]v[itex]_{s}[/itex]l

    l is the mean free path
    C[itex]_{V}[/itex] is the heat capacity at constant volume

    3. The attempt at a solution

    Rearrange the first equation to find l.

    C[itex]_{V}[/itex] can be found using some long equation that involves 'N'

    But how is N, the number of atoms supposed to be found when the question does not even tell you the mass of the sample, or what the volume of the sample is?

    Please help.
     
  2. jcsd
  3. Feb 15, 2012 #2
    Re: Estimate the mean free path of phonons in Germanium at 300K using the following d

    To calculate the heat capacity, is the Einstein model or the Debye model supposed to be used? The Einstein model, my notes say is only for optical frequencies, so can't be used in this case? But the Debye model just seems too complicated.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Estimate the mean free path of phonons in Germanium at 300K using the following data
  1. Phonon mean free path (Replies: 4)

  2. Mean free path help (Replies: 0)

Loading...