If $8.0 \ g$ of a radioactive isotope has a half-life of $10 \ hrs$. The half-life of $2.0 \ g$ of the same substance is ...... $hrs$.

The decay of $_{92}U^{235}$ is a reaction of .......... order.

The ratio of the amount of two elements $X$ and $Y$ at radioactive equilibrium is $1 : 2 \times 10^{-6}$. If the half-life period of element $Y$ is $4.9 \times 10^{-4} \ days$,then the half-life period of element $X$ will be .......... $days$.

The rate of radioactive disintegration at an instant for a radioactive sample of half-life $2.2 \times 10^{9} \ s$ is $10^{10} \ s^{-1}$. The number of radioactive atoms in that sample at that instant is:

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

$A$ piece of wood from an archaeological sample has $5.0 \text{ counts min}^{-1} \text{ g}^{-1}$ of $^{14}C$, while a fresh sample of wood has a count of $15.0 \text{ counts min}^{-1} \text{ g}^{-1}$. If the half-life of $^{14}C$ is $5770 \text{ yr}$, the age of the archaeological sample is: