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Homework Help: Isotope Ratio Problem Help!

  1. Nov 30, 2008 #1
    1. The problem statement, all variables and given/known data

    A sample of radioactive isotopes contains two different nuclides, labeled A and B. Initially, the sample composition is 1:1, i.e., the same number of nuclei A as nuclei B. The half-life of A is 2 hours and, that of B, 4 hours. What is the expected ratio A/B after 8 hours?

    2. Relevant equations

    3. The attempt a solution

    I know the number of nuclei decreases by a factor of 2 for each half life elapsed, but not sure how to go about this problem...
  2. jcsd
  3. Nov 30, 2008 #2
    Again Try N=No*(1/2)^t/T

    No = original amount of radioactive material
    N = amount of amout of radioactive material remaining after t
    t = time intercal
    T =half life

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