$_{11}Na^{24}$ has a half-life of $15 \ h$. On heating,its half-life will:

For $Ra^{226}$,the $t_{1/2}$ is $1620 \ years$. From $0.001 \ g$ of $Ra$,how many $\alpha$-particles are released per $min$?

The half-life for decay of ${}^{14}C$ by $\beta$-emission is $5730 \ yr$. The fraction of ${}^{14}C$ that decays in a sample that is $22920 \ yr$ old would be

In a radioactive decay,a uranium atom transforms into a lead atom. If a rock sample from the moon contains an equal number of uranium and lead atoms,and the half-life $(t_{1/2})$ for uranium is $4.5 \times 10^9$ years,then the age of the rock will be:

$A$ radioactive isotope has a half-life of $10 \, \text{years}$. What percentage of the original amount of it remains after $20 \, \text{years}$?

$C-14$ is used in carbon dating of dead objects because