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

The half-life period of a radioactive element is $30 \ min$. One sixteenth of the original quantity of the element will remain unchanged after ........... $min$.

The half-life of the radioactive isotope tritium $(_1^3H)$ is $12.3 \ years$. If the initial amount of tritium is $32 \ mg$,how many milligrams will remain after $49.2 \ years$ (in $mg$)?

If the quantity of a radioactive element is doubled,then its rate of disintegration per unit time will be

What is the percentage of a radioactive element decayed after $20 \ s$ if its half-life is $4 \ s$?

The half-life of $_6C^{14}$ if its decay constant $k$ or $\lambda$ is $2.31 \times 10^{-4} \ yr^{-1}$ is: