Starting with a sample of pure ${}^{66}Cu,\frac{7}{8}$ of it decays into $Zn$ in $15\, minutes$. The corresponding half life is..........$minutes$
$15$
$10$
$7\frac{1}{2}$
$5$
A sample originally contaived $10^{20}$ radioactive atoms, which emit $\alpha -$ particles. The ratio of $\alpha -$ particles emitted in the third year to that emitted during the second year is $0.3.$ How many $\alpha -$ particles were emitted in the first year?
A radioactive substance emits
A radioactive material has an initial amount $16\, gm$. After $120$ days it reduces to $1 \,gm$, then the half-life of radioactive material is ..........$days$
A radioactive nuclide is produced at the constant rate of $n$ per second (say, by bombarding a target with neutrons). The expected number $N$ of nuclei in existence $t\, seconds$ after the number is $N_0$ is given by Where $\lambda $ is the decay constant of the sample
A radioactive substance decays to $\left(\frac{1}{16}\right)^{t h}$ of its initial activity in $80\, days.$ The half life of the radioactive substance expressed in days is ... .