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!

Homework Help: Relativistic energy

  1. Feb 24, 2010 #1
    1. The problem statement, all variables and given/known data
    "A photon of energy E collides with an electron at rest. Calculate the maximum amount of Energy Ek that may be transferred to the electron. Make a graph of Ek versus E, labeling the scale in electronvolts.

    2. Relevant equations
    Transfer = Ek = E - mc^2*E/(mc^2 + 2E)

    3. The attempt at a solution
    So, I'm not sure if I have the correct equation, the reason why is:

    I take the derivative of the function and set it equal to 0

    E = -mc^2

    and then I plug that value into my function of Ek and I get 0.. but how can the max value for energy transfer be 0? I understand the -mc^2 conceptually saying perfect back scattering but I'm not sure.
  2. jcsd
  3. Feb 24, 2010 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    The energy of the outgoing photon in Compton scattering is a function of the angle. Your formula doesn't depend on the angle, so it's not a general formula for this type of scattering. Wherever you got this expression, it should explain any assumptions that went into deriving it. You need to know what those assumptions are before you use the formula. For all you know, it may not even be valid for this situation.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook