Question 206: Atoms & Nuclei

Question

A radioactive sample decays $$\frac{7}{8}$$ times its original quantity in 15 minutes. The half-life of the sample is

Accepted Answer

$$N = {{{N_0}} \over {{2^{{t \over {{T_{1/2}}}}}}}}$$
$$ \Rightarrow {2^{{t \over {{T_{1/2}}}}}} = {{{N_0}} \over N} = {{{N_0}} \over {\left( {{{{N_0}} \over 8}} \right)}} = 8$$
$$ \Rightarrow {t \over {{T_{1/2}}}} = 3$$
$$ \Rightarrow {T_{1/2}} = {{15} \over 3} = 5$$ min

Answer

5 min

Answer

7.5 min

Answer

15 min

Answer

30 min

Atoms & Nuclei

A radioactive sample decays $\frac{7}{8}$ times its original quantity in 15 minutes. The half-life of the sample is

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