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 $....\,years.$
$15$
$10$
$20$
$25$
Half life of a radioactive substance is $T$. The time taken for all the nuclei to disintegrate will be
A radioactive nuclei with decay constant $0.5/s$ is being produced at a constant rate of $100\, nuclei/s$. If at $t\, = 0$ there were no nuclei, the time when there are $50\, nuclei$ is
Define the average life of a radioactive sample and obtain its relation to decay constant and half life.
If ${N_0}$ is the original mass of the substance of half life period ${T_{1/2}} = 5$ years, then the amount of substance left after $15$ years is
Plutonium decays with a half-life of $24000 \,years$. If the plutonium is stored for $72000 \,years$, then the fraction of plutonium that remains is