The half-life of a substance is $20 \ min$. The time taken between $33\%$ decay and $67\%$ decay will be ....... $min$.

If $T$ is the half-life of a radioactive substance,then its instantaneous rate of change of activity is proportional to

At any instant,two elements $X_1$ and $X_2$ have the same number of radioactive atoms. If the decay constants of $X_1$ and $X_2$ are $10\lambda$ and $\lambda$ respectively,then the time when the ratio of their atoms becomes $\frac{1}{e}$ will be:

At time $t = 0$,a radioactive element has a mass of $10 \, gm$. What mass in $gm$ will remain after two mean lifetimes?

The decay constants of a radioactive substance for $\alpha$ and $\beta$ emission are $\lambda_{\alpha}$ and $\lambda_{\beta}$ respectively. If the substance emits $\alpha$ and $\beta$ simultaneously,then the average half-life of the material will be:

Half-life period of a sample is $15$ years. How long will it take to decay $96.875\%$ of the sample?