NEET Physics Nuclear Physics And Radioactivity NEET PYQ-Nuclear Physics

  • question_answer
    Half-life period of a radioactive substance is 6h. After 24 h activity is  \[0.01\,\mu C,\] what was the initial activity?                                                                                                                                            [AIPMT 2001]

    A)  \[0.04\,\mu C\] 

    B)       \[0.08\,\mu C\]

    C)  \[0.24\,\mu C\]

    D)                   \[0.16\,\mu C\]

    Correct Answer: D

    Solution :

    The activity of a radioactive substance is
                \[R={{R}_{0}}\,{{\left( \frac{1}{2} \right)}^{n}}\]
       Here, \[n=\] number of half-lives
                \[=\frac{t}{{{T}_{1/2}}}=\frac{24}{6}=4\]
                \[R=0.01\,\mu C\]
       Hence,
                \[0.01={{R}_{0}}{{\left( \frac{1}{2} \right)}^{4}}\]
       or      \[{{R}_{0}}=0.01\times {{(2)}^{4}}\]
                \[=0.01\times 16=0.16\,\mu C\]


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