The number of $\alpha$-particles emitted per second by a radioactive element falls to $1/32$ of its original value in $50 \ days$. The half-life period of this element is .......... $days$.

The order of a radioactive disintegration reaction is:

The half-life of $^{60}Co$ is $7 \ years$. If $1 \ g$ of it decays,the amount of the substance remaining after $28 \ years$ is (in $g$)

$A$ sample of rock from the moon contains an equal number of atoms of uranium and lead ($t_{1/2}$ for $U = 4.5 \times 10^9$ years). The age of the rock would be:

How many alpha particles are emitted per second by $1 \ \mu g$ of radium?

$A$ freshly prepared radioactive element has a half-life of $2 \ hr$. It emits radiation whose intensity is $64$ times the permissible safe level. The minimum time after which it would be possible to work with this sample is .......... $hr$.