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Homework Help: De Broglie Wavelengths: Need clarification for questions.

  1. Feb 27, 2008 #1
    Thanks for any help you can give. I just started modern physics and my teacher has a tendency to give questions that were based on things not mentioned in the book and only briefly mentioned in the lectures, so I'm a bit confused.

    1. The problem statement, all variables and given/known data

    1) Calculate the distribution function of the de Broglie wavelengths of atoms in the thermal equilibrium gas. The gas temp. is T and the atomic mass is M. What is the most probable de Broglie wavelength?

    2)A neutron moves between two parallel impenetrable walls and the neutron velocity stays perpendicular to the wall surfaces. Distance between the walls is L = 1000 Å. Determine all allowed kinetic energies of a neutron, if its motion is described by standing de Broglie waves.

    2. Relevant equations

    3. The attempt at a solution

    1) While I would love to attempt the solution. What is "the thermal equilibrium gas"? I've never heard the term before and I couldn't find anything on google about it.

    2) I think I know how to solve the problem, the wavelength cannot be greater the spacing between the walls, but the formula given uses "Å" as the units, and I'm not sure what the "Å" means.

    I had the same Physics prof for two straight years, and he always gave problems directly from the book, so I'm not used to not being able to directly reference back to stuff.
    Last edited: Feb 27, 2008
  2. jcsd
  3. Feb 27, 2008 #2
    That A thing is the symbol for an angstrom, 10^-10 I think

    For the first one I think they're saying the gas is at thermal equilibrium, so you can say the average kinetic energy = 3/2*K*T
  4. Feb 27, 2008 #3
    Thank you so much--especially with the first one. Now I can actually do the problems.
  5. Feb 28, 2008 #4
    Distribution of molecular velocities in termal equilibrium gas is Maxwell-Boltzmann distribution.
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