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Homework Help: Which halflife formula is correct?

  1. Apr 11, 2005 #1
    Which half - life formula is correct? Please help

    is it
    Al = Ao(1/2)^(t/h)
    Al = Ao(1/2)^(h/t)
    where Ao =original amount
    Al = amount left
    Last edited: Apr 11, 2005
  2. jcsd
  3. Apr 11, 2005 #2


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    Science Advisor

    Well, what do YOU think? Suppose t were equal to 2h.

    The first formula gives AI= Ao(1/2)^(2h)= Ao((1/2)^h)^2 which is less than the amount at the half life.

    The second formula gives AI= A0(1/2)^(h/2)= A0((1/2)^h)^(1/2) which is more than the amount at the half life.

    If you let this (radioactive subtance?) sit longer, will it gain or lose mass?
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