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Pair production question,

  1. Apr 19, 2010 #1
    1. The problem statement, all variables and given/known data
    If positron and electron have the same rest energy can pair production occur?


    2. Relevant equations
    E=hc/λ plancks equation
    E=mc^2


    3. The attempt at a solution
    so i found the E of the photons using plancks equation
    and found the photon E to be 6.83x10^-14 ( should I double this due to two photons required?)
    so
    for pair production the energy of the photons has to be at least the energy of mc^2
    so i just added the positron and electrons masses and multiplied by c^2
    and got 1.64x10^-13
    did i do this correctly? so Ephoton < E of Positron and electron so no pair production can occur?
    am i missing anything or do something wrong?
     
    Last edited: Apr 19, 2010
  2. jcsd
  3. Apr 19, 2010 #2

    vela

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    You still seem to be leaving out information. Could you please post the entire text of the problem?
     
  4. Apr 19, 2010 #3
    heres the first part
    A. Use wiens law to determine the peak wavelength of blackbody photons where T = 10^9K
    so λ= 2.9x10^-3 / 10^9
    => λ = 2.9x10^-12
    then
    B. use planck Eq to determine the energy of the photons
    E = hc/λ => E = (6.6x10^-25)(3x10^8)/ 2.9x10^-12 => E = 6.83x10^-14

    C. The positron and electron where created by pair production (ie. Photon + photon --> Positron + Electron). If Both positron and electron have the same "rest energy" show whether or pair production can occur.
    I tried using E=mc^2
    I know that the energy of the photns must be atleast the energy of the posi and electron.
    so mc^2 is the energy of the electron and positron.
    used m as (9.109x10^-31)x2 since the positron and electron have the same mass.
     
    Last edited: Apr 19, 2010
  5. Apr 19, 2010 #4

    vela

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    You need to include units on your numbers. You've calculated the individual energies correctiy. You just need to make sure the initial energy exceeds the minimum energy of electron-positron pair.
     
  6. Apr 19, 2010 #5
    ok il make sure to add units,
    just for clarification is the E i calculated in step B the initial ? and if it's not larger they cant be formed right?

    thanks for all the help!
     
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