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Homework Help: Percentage transmittance gamma ray through lead

  1. May 25, 2017 #1
    1. The problem statement, all variables and given/known data
    I = Io e-ux.PNG

    2. Relevant equations
    I = Io e^-ux

    3. The attempt at a solution
    0.75 = 1 * e^-u1
    using algebra... u =2.117

    I = 1 * e^-2.117*3
    I = 0.00175

    Answer is apparently 42.2. Can someone tell me where i went wrong? Thanks for any help as always
  2. jcsd
  3. May 25, 2017 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    Check your math. When I put ##e^{-2.117}## into my calculator, I don't get 0.75.
  4. May 25, 2017 #3
    omfg i got it. thanks a lot i derped out with the log rules.
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