Question

A certain radioactive isotope has leaked into a small stream. Two hundred days after the leak, 15% of the original amount of the substance remained. Determine the half-life of this radioactive isotope.

Answer 1

the fundamental decay equation is: \( N(t) = N_0 e^{- k t}\)

the steps:

find k from the first data point, viz \(N(200) = 0.15 N_o = N_0 e^{- k( 200)}\)

then, use same equation to calc half life \(T\):

\(N(T) = 0.5 * N_o = N_o e^{-k T}\)

Answer 2

Great! Thanks--I was on the right track.