The half-life $(T)$ and the disintegration constant $(\lambda)$ of a radioactive substance are related as:

Two radioactive substances $A$ and $B$ have decay constants $5 \lambda$ and $\lambda$ respectively. At $t=0$, they have the same number of nuclei. The ratio of the number of nuclei of $A$ to that of $B$ will be $(1/e)^2$ after a time interval of:

The half-life of radon is $3.8 \ days$. Three-fourths of a radon sample decays in ............ $days$.

If the half-life of a radioactive sample is $10\, hours$,its mean life is .......... $hours$.

If a radioactive substance reduces to $\frac{1}{16}$ of its original mass in $40$ days,what is its half-life in days?

If $T$ is the half-life of a radioactive material,then the fraction that would remain after a time $\frac{T}{2}$ is