Radioactive lead $_{82}Pb^{201}$ has a half-life of $8 \ hours$. Starting from $1 \ mg$ of this isotope,how much will remain after $24 \ hours$?

For $Ra^{226}$,the $t_{1/2}$ is $1620 \ years$. From $0.001 \ g$ of $Ra$,how many $\alpha$-particles are released per $min$?

$A$ radioactive isotope having a half-life of $3 \ days$ was received after $12 \ days$. It was found that there were $3 \ g$ of the isotope in the container. The initial weight of the isotope when packed was ......... $g$.

$A$ radioactive element has a half-life of $1 \text{ day}$. After $3 \text{ days}$,the amount of the element left will be:

The half-life of $_6C^{14}$ if its decay constant $k$ or $\lambda$ is $2.31 \times 10^{-4} \ yr^{-1}$ is:

The half-life of $C^{14}$ is $5760 \ years$. For a $200 \ mg$ sample of $C^{14}$, the time taken to change to $25 \ mg$ is (in $years$)