The nuclear activity of a radioactive element becomes $\left(\frac{1}{8}\right)^{\text {th }}$ of its initial value in $30\, years.$ The half-life of radioactive element is $....\,years.$
$15$
$10$
$20$
$25$
Give a brief explanation about radioactivity.
The half-life of a radioactive nucleus is $5$ years, The fraction of the original sample that would decay in $15$ years is
The half-life of a radioactive element $A$ is the same as the mean-life of another radioactive element $B.$ Initially both substances have the same number of atoms, then
A radioactive sample $\mathrm{S} 1$ having an activity $5 \mu \mathrm{Ci}$ has twice the number of nuclei as another sample $\mathrm{S} 2$ which has an activity of $10 \mu \mathrm{Ci}$. The half lives of $\mathrm{S} 1$ and $\mathrm{S} 2$ can be
Alpha rays emitted from a radioactive substance are