Which halflife formula is correct?

huan.conchito

is it
Al = Ao(1/2)^(t/h)
or
Al = Ao(1/2)^(h/t)
?
where Ao =original amount
Al = amount left

HallsofIvy

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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huan.conchito	Which halflife formula is correct? Tweet is it Al = Ao(1/2)^(t/h) or Al = Ao(1/2)^(h/t) ? where Ao =original amount Al = amount left

HallsofIvy Recognitions: Gold Member Science Advisor Staff Emeritus	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?