The half-life of ${ }^{198} {Au}$ is $3 \,days.$ If atomic weight of ${ }^{198} {Au}$ is $198\, {g} / {mol}$ then the activity of $2 \,{mg}$ of ${ }^{198} {Au}$ is ..... $\times 10^{12}\,disintegration/second$
$2.67$
$16.18$
$6.06$
$32.36$
Half-life is measured by
A radioactive material has a half-life of $8$ years. The activity of the material will decrease to about $1/8$ of its original value in .......... $years$
Out of the following, which one is not emitted by a natural radioactive substance?
Activity of radioactive element decreased to one third of original activity ${R_0}$ in $9$ years. After further $9$ years, its activity will be
The half life of a radioactive substance is $5$ years. After $x$ years a given sample of the radioactive substance gest reduced to $6.25 \%$ of its initial value of $x$ is ...............