Q 12-13-122JEE MainJEE Main 2019 (10 Jan, Shift 1)Easy
Using a nuclear counter the count rate of emitted particles from a radioactive source is measured. At $t = 0$ it was $1600$ counts per second and at $t = 8$ seconds it was $100$ counts per second. The count rate observed, as counts per second, at $t = 6$ seconds is close to:
Answer: (B) $200$
$\dfrac{1600}{100} = 16 = 2^4$, so $8\ \text{s}$ is four half-lives and $T_{1/2} = 2\ \text{s}$.
At $t = 6\ \text{s}$ (three half-lives): $\dfrac{1600}{2^3} = 200$ counts per second.
Solution by Sreeraj P, M.Sc Physics