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JEE Main & Advanced Sample Paper JEE Main Sample Paper-7

  • question_answer
    The count rate of 100 cc of a radioactive liquid is R. After removing some liquid, the count rate becomes R/10 after three half-lives. The initial volume of the liquid available after removing some liquid is

    A)  20 cc                    

    B)  40 cc

    C)  60 cc                                    

    D)  80 cc

    Correct Answer: D

    Solution :

    After three half-lives, the number of nuclei should be \[{{N}_{3}}={{N}_{i}}{{\left( \frac{1}{2} \right)}^{3}}\]. Since \[R\propto N\] we have, \[{{R}_{3}}=\frac{R}{10}\] makes \[{{N}_{i}}=80cc\].


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