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Compton Scattering Question

  1. Oct 14, 2007 #1
    1. The problem statement, all variables and given/known data
    If the maximum energy transferred to an electron during Compton Scattering is 50KeV, what is the wavelength of the incident photon?

    2. Relevant equations
    [tex]\lambda[/tex]' - [tex]\lambda[/tex][tex]_{o}[/tex] = h/(Me*c)(1-cos[tex]\theta[/tex])

    3. The attempt at a solution
    We know that the maximum energy transfer for compton scattering occurs when:
    [tex]\theta[/tex] = 180
    [tex]\phi[/tex] = 0

    So when [tex]\theta[/tex]=180
    [tex]\lambda[/tex]' - [tex]\lambda[/tex][tex]_{o}[/tex] = 0.00486nm

    Everything I've tried looking up involves the scattered photon as well (like the momentum, energy, wavelength equations)

    Any tips on where to look/where I can go next?
  2. jcsd
  3. Oct 14, 2007 #2


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    Staff: Mentor

    Apply the conservation of momentum and energy.

    One has the energy of the electron, from which one can obtain the momentum.

    pph = E/c
  4. Oct 14, 2007 #3
    I'm still stuck at finding the momentum of the electron. I know it's going to have 50 000ev of Kinetic Energy, but I'm not sure how to relate it to momentum.
  5. Oct 14, 2007 #4


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    Staff: Mentor

    One could do it either classically, e.g. p = mv and KE = 1/2 mv2 = 1/2 p2/m, where m is the rest mass, or relativistically where m = [itex]\gamma[/itex]mo, taking into account the change in mass with velocity.

    50 keV is ~0.1 of the rest energy 0.511 MeV.
  6. Sep 2, 2010 #5


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    I can't solve this problem too!!! Please help me!!! I am taking exams next week and i 'm supposed to know what happens!!! my prof gave us a little help by saying these:

    1). 1239.8/E=.... (and i think from this we have λο)
    2). ΔΕ -> Εφ=Εφ'+Εmax(e) -> 50keV=Εφ-Εφ' (where Eφ=photon's energy)
    3) θ=π since (1-cosθ)=max

    Can anybody help???????
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