In a radioactive disintegration, the ratio of initial number of atoms to the number of atoms present at an instant of time equal to its mean life is
$1/e^2$
$1/e$
$e$
$e^2$
The half-life of $^{215}At$ is $100\mu s$. The time taken for the radioactivity of a sample of $^{215}At$ to decay to $\frac{{1}}{{16}} \,th$ of its initial value is .........$\mu s$
What is the half-life (in years) period of a radioactive material if its activity drops to $1 / 16^{\text {th }}$ of its initial value of $30$ years?
Define the disintegration rate or radioactivity of a sample and obtain the relation $R = \lambda N$ and define its different units.
Age of a tree is determined using radio-isotope of
Two radioactive materials $A$ and $B$ have decay constant $5\lambda$ and $\lambda$ respectively.At $t=0$ they have the same number of nuclei, then the ratio of the number of nuclei of $A$ to that $B$ will be $(1/e)^2$ after a time interval