The decay of a radioactive material is shown in the graph. From the graph,the decay constant of the material is nearly (in $h^{-1}$)

If $f$ denotes the ratio of the number of nuclei decayed $(N_{d})$ to the number of nuclei at $t=0$ $(N_{0})$,then for a collection of radioactive nuclei,the rate of change of $f$ with respect to time is given as: [$\lambda$ is the radioactive decay constant]

Two radioactive materials $A$ and $B$ have decay constants $25 \lambda$ and $16 \lambda$ respectively. If initially they have the same number of nuclei,then the ratio of the number of nuclei of $B$ to that of $A$ will be $e$ after a time $t = \frac{1}{a \lambda}$. The value of $a$ is $......$

If the half-life of an element is $69.3 \text{ hours}$,what percentage of it will decay between the $10^{\text{th}}$ and $11^{\text{th}}$ hours? (Initial activity $= 50 \mu Ci$)

$A$ radioactive sample $S_1$ having an activity $5 \mu Ci$ has twice the number of nuclei as another sample $S_2$ which has an activity of $10 \mu Ci$. The half-lives of $S_1$ and $S_2$ can be

In a mean life of a radioactive sample,