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NEET Physics Nuclear Physics And Radioactivity NEET PYQ-Nuclear Physics

  • question_answer
    The half-life of a radioactive isotope X is 50 yr. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be                                                                                                                         [AIPMT (S) 2011]

    A)  200 yr          

    B)       250 yr

    C)  100 yr           

    D)       150 yr

    Correct Answer: A

    Solution :

    We know that
                \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{t/{{t}_{1}}/2}}\]
                \[\left( \frac{1}{16} \right)={{\left( \frac{1}{2} \right)}^{t/50}}\]
                \[t=4\times 50\]
                \[t=200yr\]


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