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JIPMER Jipmer Medical Solved Paper-1996

  • question_answer
    A certain radioactive element has a half-life of 20 years. If you had a block with 10 g of the element in it, after how many years will there be just 2.5 g of the element in the block?

    A)  40 years

    B)                                         60 years             

    C)         80 years             

    D)         100 years

    Correct Answer: A

    Solution :

    Here \[N=2.5g,\] \[{{N}_{0}}=10g\] \[n=\frac{N}{{{N}_{0}}}=\frac{2.5}{10}=\frac{1}{4}={{\left( \frac{1}{2} \right)}^{2}}\] Again \[{{\left( \frac{1}{2} \right)}^{2}}={{\left( \frac{1}{2} \right)}^{n}}\]so, \[n=2\] The year after which it will decay \[=2\times {{T}_{1/2}}=2\times 20=40\,years\]


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