The activity of a radioactive sample falls from 700 s–1 to 500 s–1 in 30 minutes. Its half life is close to:
Solution
A = A<sub>0</sub> e<sup>-$\lambda$t</sup>
<br><br>$\Rightarrow$ 500 = 700 e<sup>-$\lambda$$\times$30</sup>
<br><br>$\Rightarrow$ $\ln {7 \over 5}$ = $\lambda$$\times$30
<br><br>Also T<sub>1/2</sub> = ${{\ln 2} \over \lambda }$ = ${{\ln 2} \over {\ln {7 \over 5}}} \times 30$
<br><br>$\Rightarrow$ T<sub>1/2</sub> = 62 min
About this question
Subject: Physics · Chapter: Atoms and Nuclei · Topic: Radioactivity
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