J & K CET Engineering J and K - CET Engineering Solved Paper-2015

  • question_answer
    What amount of original radioactive material is left?

    A) \[6.5%\]             

    B) \[12.5%\]

    C) \[25.5%\]             

    D) \[33.3%\]

    Correct Answer: B

    Solution :

    Amount of radioactive material left is \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\] Where n = number of half-lives. \[=3\] \[{{N}_{0}}\]= original amount of the radioactive material. \[\Rightarrow \] \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{3}}=\frac{{{N}_{0}}}{8}\] \[=\frac{100}{8}%\] Of \[{{N}_{0}}=125%\] of \[{{N}_{0}}\]


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