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JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2011

  • question_answer
        The half of\[^{215}At\]is 100 as. The time taken for the radioactivity of a sample of 215 At to decay to 1/ 16th of its initial value is

    A)  400 as                                  

    B)  6.3 as

    C)  40 as                                    

    D)  30 as

    Correct Answer: A

    Solution :

                    \[N={{N}_{0}}.{{\left( \frac{1}{2} \right)}^{T/{{T}_{1/2}}}}\] \[\left( \frac{1}{16} \right)={{\left( \frac{1}{2} \right)}^{T/{{T}_{1/2}}}}\]                 \[{{\left( \frac{1}{2} \right)}^{4}}={{\left( \frac{1}{2} \right)}^{T/{{T}_{1/2}}}}\]                 \[\frac{T}{{{T}_{1/2}}}=4\]                 \[\frac{T}{100}=4\Rightarrow T=400\,\,\mu s\]


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