The variation of decay rate with the number of active nuclei is correctly shown in which graph?

The half-life of a radioactive nuclide is $100 \, hours$. The fraction of original activity that will remain after $150 \, hours$ would be:

If $t_{1/2}$ is the half-life of a substance,then $t_{3/4}$ is the time in which the substance:

The half-life of a radioactive substance is $20 \text{ minutes}$. In $........ \text{ minutes}$ time,the activity of the substance drops to $\left(\frac{1}{16}\right)^{th}$ of its initial value.

$N$ atoms of a radioactive element emit $n$ number of $\alpha$-particles per second. The mean life of the element in seconds is:

The half-life of a radioactive sample,where the initial activity of the material was $8 \text{ counts}$ and after $3 \text{ hours}$ it becomes $1 \text{ count}$,is ............... $hours$.