If the half-life of a substance is $3.8\, days$ and its initial quantity is $10.38\, gm$,then the quantity of the substance remaining after $19\, days$ will be ........$gm$.

$A$ radioactive element has a half-life of $15$ years. What is the fraction that will decay in $30$ years?

If $N_t = N_o e^{-\lambda t}$,then the number of nuclei decaying between time $t_1$ and $t_2$ $(t_2 > t_1)$ is given by:

What fraction of a radioactive material will get disintegrated in a period of two half-lives?

$A$ radioactive nucleus decays by two different processes. The half-life of the first process is $5$ minutes and that of the second process is $30\,s$. The effective half-life of the nucleus is calculated to be $\frac{\alpha}{11}\,s$. The value of $\alpha$ is $..............$

The rate of disintegration was observed to be $10^{17}$ disintegrations per second when its half-life period is $1445$ years. The original number of particles is: