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Homework Help: Neutron diffraction

  1. Jan 18, 2012 #1
    1. The problem statement, all variables and given/known data
    In an experimental setup (shown in attachment) like this for neutron diffraction, how do I find the wavelength of the neutron. It should be around 2nm.

    2. Relevant equations

    [tex] \lambda = \frac{h}{mv}=\frac{396}{v} [/tex]

    3. The attempt at a solution

    I am having trouble with finding v of the neutron. Does it have to do with the total length of the tube?

    Attached Files:

  2. jcsd
  3. Jan 19, 2012 #2
    The only speed information in your diagrams states that the neutrons are 'thermal' neutrons. This means that they are in thermal equilibrium with the moderator.
    In an online reference site I read that neutrons have a range of speeds but the accepted speed for thermal neutrons is 2200 m/s.
    In the absence of any other information I would use this and at least get some sort of answer.
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