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CMC Medical CMC-Medical VELLORE Solved Paper-2015

  • question_answer
    Approximately how many half-life periods must be elapsed if the activity of a radioactive isotope sample is to be reduced to 0.004 of the original value?

    A)  8                                            

    B)  4

    C)  6                                            

    D)  5

    E)  9

    Correct Answer: A

    Solution :

                    The ratio of activities is \[\frac{A}{{{A}_{0}}}={{\left( \frac{1}{2} \right)}^{n}}\Rightarrow 0.004={{\left( \frac{1}{2} \right)}^{n}}\] \[\Rightarrow \]               \[\frac{1}{250}={{\left( \frac{1}{2} \right)}^{n}}\]                 \[n=8\]


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