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Punjab Medical Punjab - MET Solved Paper-2004

  • question_answer
    Rn decay into \[{{P}_{o}}\] by emitting \[\text{ }\!\!\alpha\!\!\text{ -}\]particles with half-life of 4 days a sample contains \[6.4\times {{10}^{10}}\] atom of Rn. After 12 days, the number of atoms of Rn left in the sample will be:

    A) \[0.8\times {{10}^{10}}\]

    B) \[2.1\times {{10}^{10}}\]

    C) \[3.2\times {{10}^{10}}\]

    D) \[0.3\times {{10}^{10}}\]

    Correct Answer: A

    Solution :

    Number half-life                 \[n=\frac{12}{4}=3\] This fraction undecided                 \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{3}}=\frac{1}{8}\] So,          \[N=\frac{1}{8}{{N}_{0}}=\frac{1}{8}\times 6.4\times {{10}^{10}}\]                 \[=0.8\times {{10}^{10}}\]


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