Q 12-13-060JEE MainJEE Main 2023 (29 Jan, Shift 1)Easy
If a radioactive element having half-life of $30\ \text{min}$ is undergoing beta decay, the fraction of radioactive element that remains undecayed after $90\ \text{min}$ will be
Answer: (A) $\dfrac18$
$90\ \text{min}$ is $3$ half-lives: $\dfrac{N}{N_0}=\left(\dfrac12\right)^3=\dfrac18$.
Solution by Sreeraj P, M.Sc Physics