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13.Nuclei
medium
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 $t = 8\, seconds$ it was $100$ counts per second. The count rate observed, as counts per second, at $t = 6\, seconds$ is close to
A
$200$
B
$150$
C
$400$
D
$360$
(JEE MAIN-2019) (AIEEE-2012)
Solution
In $8$ seconds count rate becomes $\frac{1}{16}$ times.
$\therefore $ $4 $ half lives $=8\,s$
$1$ half lie $=2 \mathrm{s}$
In $6 \mathrm{s}$ or $3$ half lives, count rate $=\frac{1600}{2^{3}}=200$
Standard 12
Physics
