A piece of wood from a recently cut tree shows $20\,decays$ per minute. A wooden piece of same size placed in a museum ( obtained from a tree cut many years back) shows $2\,decays$ per minute. If half life of $C^{14}$ is $5730\, years$, then age of the wooden piece placed in the museum is approximately ........... $years$
$10439$
$13094$
$19039$
$39049$
The graph between number of decayed atoms $N'$ of a radioactive element and time $t$ is
In a radioactive decay chain reaction, ${ }_{90}^{230} Th$ nucleus decays into ${ }_{84}^{214} Po$ nucleus. The ratio of the number of $\alpha$ to number of $\beta^{-}$particles emitted in this process is. . . . .
The curve between the activity $A$ of a radioactive sample and the number of active atoms $N$ is
If $10\%$ of a radioactive material decays in $5\, days$ then the amount of the original material left after $20\, days$ is approximately .......... $\%$
Unit of radioactivity is Rutherford. Its value is