Carbon dating is best suited for determining the age of fossils if their age in years is of the order of

In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life ………. $\%$

Which sample contains greater number of nuclei : a $5.00- \mu Ci$ sample of $_{240}Pu$ (half-life $6560\,y$) or a $4.45 – \mu Ci$ sample of $_{243}Am$ (half-life $7370\, y$)

If half-life of a radioactive atom is $2.3\, days$, then its decay constant would be

At $t = 0$, number of active nuclei in a sample is $N_0$. How much no. of nuclei will decay in time between its first mean life and second half life?