Question

One of the many by products of uranium is radioactive plutonium, which has a half life of approximatley 25000 ytears. if some of this putonium is encased in concrete, what fraction of it will remain after 100 years?

Answer 1

Answer:

0.9972 fraction of plutonium will remain after 100 years.

Explanation:

Half life of plutonium = $t_{1/2}=25000 years$

Let the initial mass of plutonium be = $A_o$

Mass of plutonium after time of 100 years = A

Decay constant for this process = $\lambda =\frac{0.693}{t_{1/2}}$

$A=A_o\times e^{-\lambda t}$

$A=A_o\times e^{-\frac{0.693}{25000 years}\times 100 year}$

$A=A_o\times 0.9972$

$\frac{A}{A_o}=0.9972$

0.9972 × 100 = 99.72 %

0.9972 fraction of plutonium will remain after 100 years.