The disintegration constant for a radioactive substance is $0.58 \, hr^{-1}$. Its half-life period is $........ \, hr$.

$A$ radioactive sample $(Z = 22)$ decreases by $90\%$ in $10 \ \text{years}$. What will be the half-life of the sample in $\text{years}$?

$C-14$ is used in carbon dating of dead objects because

$A$ radioactive isotope having $t_{1/2} = 3 \ days$ was measured after $12 \ days$. If $3 \ g$ of the isotope remains in the container,what was the initial weight of the isotope (in $g$)?

If $87.5\%$ of a given substance disintegrates in $40 \text{ minutes}$,what is the half-life of the radioactive substance?

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