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NEET AIPMT SOLVED PAPER SCREENING 2011

  • 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

    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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