The half life of a radioactive sample undergoing α -decay is 1.4 × 10¹⁷ s. If the number of nuclei in the sample is 2.0 × 10²¹, the activity of the sample is nearly (a) 10³ Bq (b) 10⁴ Bq (c) 10⁵ Bq (d) 10⁶ Bq

Answer: (b). A = λ N = (0.693)/(T)N. A = 0.693×2.0×10²¹1.4×10¹⁷ ≈ 0.99×10⁴ Bq. So the answer is (b) 10⁴ Bq.

The half life of a radioactive sample undergoing α -decay is 1.4 ×… | NEET 2020 (Phase 2)

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Law of Radioactive Decay

The half life of a radioactive sample undergoing $\alpha$ -decay is $1.4 \times 10^{17}\text{ s}$ . If the number of nuclei in the sample is $2.0 \times 10^{21}$ , the activity of the sample is nearly

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Answer: (b)

$A = \lambda N = \frac{0.693}{T}N$ .
$A = \frac{0.693\times2.0\times10^{21}}{1.4\times10^{17}} \approx 0.99\times10^4$ Bq.
So the answer is (b) $10^4$ Bq.

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