From $N$ atoms of a radioactive element,$n$ alpha particles are emitted per second. The half-life of the element is ......

Ten percent of a radioactive sample has decayed in $1$ day. After $2$ days,the decayed percentage of nuclei will be ...... $\%$

$99\%$ of the nuclei of a radioactive element decay between which of the following times?

$A$ radioactive nucleus with a decay constant $\lambda = 0.5/s$ is being produced at a constant rate of $P = 100\, nuclei/s$. If at $t = 0$ there were no nuclei,the time when there are $N = 50\, nuclei$ is:

The initial activity of a certain radioactive isotope was measured as $16000 \ counts \ min^{-1}$. Given that the only activity measured was due to this isotope and that its activity after $12 \ h$ was $2000 \ counts \ min^{-1}$,its half-life,in hours,is nearest to

Radon-$222$ has a half-life of $3.8$ days. If one starts with $0.064 \ kg$ of radon-$222$, the quantity of radon-$222$ left after $19$ days will be (in $kg$)