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13.Nuclei
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The half life of a radioactive sample undergoing $\alpha$ - decay is $1.4 \times 10^{17}$ s. If the number of nuclei in the sample is $2.0 \times 10^{21}$, the activity of the sample is nearly
A
$10^{3} \;Bq$
B
$10^{4}\;Bq$
C
$10^{5}\;Bq$
D
$10^{6}\;Bq$
(NEET-2020)
Solution
The activity (A) is defined as the rate of decay of radioactive substance.
$A=-\frac{d N}{d t}=N \lambda$
$A = N \times \frac{0.693}{ T } \quad[ T$ is half life $]$
$A=2 \times 10^{21} \times \frac{0.693}{1.4 \times 10^{17}}$
$A=10^{4} B q$
Standard 12
Physics
