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Homework Help: Calculating Half-life

  1. Apr 15, 2009 #1
    1. The problem statement, all variables and given/known data
    If a patient is given a radioactive isotope which has a half-life of six days and a biological half-life of ten days, what is the effective half-life for the isotope.

    2. Relevant equations

    I know the formula for half-life calculations is T1/2 = 0.693/k

    3. The attempt at a solution

    I don't know where to start with this. My tutor just briefly went over it. It was a question on a past paper so I just want it covered in case it comes up in my exams.

    Any help I'd be grateful. Thanks.
  2. jcsd
  3. Apr 15, 2009 #2


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    Homework Helper

    For what you are asking I think it works something like this:

    N = No*e-t/T1*e-t/T2 = No*e-t/T1+t/T2 = No*et/T

    Where 1/T = 1/T1 + 1/T2
    Last edited: Apr 15, 2009
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