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Homework Help: Energy of a photon absorbed by an elementary particle

  1. Sep 16, 2012 #1
    1. The problem statement, all variables and given/known data
    An elementary particle of mass M completely absorbs a photon, after which its mass is 1.01M.
    a) What was the energy of the incoming photon?
    b) Why is that energy greater than 0.01Mc2?

    2. Relevant equations

    E = mc2 or Δm = Δ E/c2
    E = γmc2

    3. The attempt at a solution

    The only thing I can see doing is Δm = 1.01M - M = 0.01M = E/c2
    But that gives E = 0.01Mc2 , which according to part b is not the answer. How do you solve this?
  2. jcsd
  3. Sep 16, 2012 #2
    After further reading, I'll add these equations:
    (mc2)2 = E2 - (pc)2
    E = pc (for m = 0)
  4. Sep 16, 2012 #3
    OKAY. so I got an answer of 0.01005Mc^2, so I'd appreciate if someone could check/correct that for me. I still don't know how to explain it in part b.
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