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NEET Sample Paper NEET Sample Test Paper-93

  • question_answer
    The activity of a radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes. The decay constant is approximately

    A) 0.922 per minute

    B)        0.691 per minute

    C) 0.461 per minute

    D)        0.230 per minute

    Correct Answer: C

    Solution :

    [c] \[\frac{dN}{dt}=KN\] \[9750=K{{N}_{0}}\]                ...(1) \[975=KN\]                    ...(2) Dividing (l) by (2) \[\frac{N}{{{N}_{0}}}=\frac{1}{10}\] \[K=\frac{2.303}{t}\log \frac{{{N}_{0}}}{N}=\frac{2.303}{5}\log 10\] \[=0.4606=0.461\]per minute


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