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Compton Effect Problem

  1. Jun 18, 2012 #1
    Hey, I was just wondering if someone could give me feedback on a problem. For some reason the answer is not in the back of the text.

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

    An x-ray with a wavelength of 2.5 x 10-8 m is absorbed by a stationary electron. Determine the final velocity of the electron.
    Vxray=3.0x10^8 m/s
    melectron= 1.602x10^-19kg

    2. Relevant equations
    Velectron(after)= Vxray((2(h/cλ))/(melectron+(h/cλ)))

    3. The attempt at a solution

    V(electronafter)= (3.0x10^8)((2((6.626x10^-34)/(3.0x10^8)(2.5x10^-8))/(1.602x10^-19)((6.626x10^-34)/(3.0x10^8)(2.5x10^-8)))

    v(electronafter)= 3.31x10^-7m/s

    Sorry if the formula is hard to understand, I used the formula for conservation of momentum in an elastic collision where one object is stationary before the collision.
    Last edited: Jun 18, 2012
  2. jcsd
  3. Jun 18, 2012 #2


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    Your problem statement doesn't mention a proton. How does it come into the problem?
  4. Jun 18, 2012 #3
    Sorry anywhere it says proton it should say electron.
  5. Jun 18, 2012 #4


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    A solitary electron cannot absorb a photon. (Also if it did, it would be an inelastic collision, not an elastic collision.) If this problem is about the Compton effect, the photon scatters off the stationary electron.

    Your value for the mass of the electron isn't correct.
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