NEET Physics Nuclei Questions Solved

The activity of a radioactive sample is measured as $N_0$ counts per minute at t = 0 and $N_0/e$ counts per minute at t = 5 min. The time (in minute) at which the activity reduces to half its value is [2010]

(1) ${\log }_e 2/5$          (2) $\frac{5}{{\log }_{e}2}$           (3) $5 {\log }_{10} 2$        (4) $5 {\log }_e 2$