If the half-life of a radioactive element is $12.5 \ h$,then the time taken to disintegrate $256 \ g$ of the substance into $1 \ g$ is (in hours)

The activity of a radioactive substance can be represented by various units. Select the correct option.

$A$ radioactive material decays by simultaneous emissions of two particles with half-lives of $1400 \, years$ and $700 \, years$ respectively. What will be the time after which one-third of the material remains? (Take $\ln 3 = 1.1$) (In $years$)

For a substance,the fraction of its initial quantity $(N_0)$ which will disintegrate in its average lifetime is about $(e = 2.71)$.

$A$ radioactive sample has a half-life of $5$ years. The probability of decay in $10$ years will be ........$\%$

The activity of a sample of a radioactive material is ${A_1}$ at time ${t_1}$ and ${A_2}$ at time ${t_2}$ $({t_2} > {t_1})$. If its mean life is $T$,then: