$10 \ g$ of a radioactive element is disintegrated to $1 \ g$ in $2.303 \ \text{minutes}$. What is the half-life (in minutes) of that radioactive element?

$A$ 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 .......... $hr$.

$A$ radioactive element has a half-life of $1 \text{ day}$. After $3 \text{ days}$,the amount of the element left will be:

If the half-life of a certain radioactive nucleus is $1000 \ s,$ the disintegration constant is

The half-life period of ${}_{53}I^{125}$ is $60$ days. The radioactivity after $180$ days will be (in $\%$)

$A$ certain nuclide has a half-life period of $30 \ min$. If a sample containing $600$ atoms is allowed to decay for $90 \ min$,how many atoms will remain (in $atoms$)?