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Homework Help: Rate of radiation coming from inside a container

  1. Jul 26, 2008 #1
    1. The problem statement, all variables and given/known data

    A aluminum container has walls that are 23 mm thick. A radiation detector measures a rate of 542 Hz outside the container. The radiation source inside the container has a half-life of 2.4 years. What is the rate of radiation from the source inside the container?

    2. Relevant equations


    u= 0.014 mm-1
    x1/2=48.26 mm

    3. The attempt at a solution
    I tried to solve this problem using proportions, and it didn't work. Is there another way?

    23 mm is 47% of aluminums half-length (48.36 mm). so the amount of radiation change from inside to outside should be 50% of 47% of aluminums half-lenght.

    so 542*23.5% = 127.3

    542+127.3 = 669.3 Hz
  2. jcsd
  3. Jul 27, 2008 #2
    Proportion doesn't work here. You should use the exponential law of decrease in intension:

    [tex]I = I_0 2^{l/L}[/tex]

    where [tex]l[/tex] is the lenght of absorbing material and [tex]L[/tex] is the half-lenght.
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