$A$ radioactive sample is emitting $64$ times more radiation than the non-hazardous limit. If its half-life is $2 \ hr$,after what time will it become non-hazardous? $(hr)$

The half-life period of $Pb^{210}$ is $22 \ years$. If $2 \ g$ of $Pb^{210}$ is taken,then after $11 \ years$ how much of $Pb^{210}$ will be left in $g$?

$2 \text{ g}$ of a radioactive sample having a half-life of $15$ days was synthesized on $1^{st}$ Jan $2009$. The amount of the sample left behind on $1^{st}$ March $2009$ (including both the days) is: (in $\text{ g}$)

Half-life of a radioactive substance which disintegrates by $75\%$ in $60 \ min$ will be ......... $min$.

$A$ piece of wood was found to have the $C^{14}/C^{12}$ ratio $0.7$ times that in a living plant. The time period when the plant died is ....... $years$ (Half-life of $C^{14} = 5760 \, yrs$).

The half-life of radioisotopic bromine $-82$ is $36 \ hours$. The fraction which remains after one day is . . . . . . $\times 10^{-2}$. (Given $\text{antilog } 0.2006 = 1.587$)