CET Karnataka Medical CET - Karnataka Medical Solved Paper-2000

  • question_answer
    After an interval of one day, 1/6th of the initial amount of a radioactive material remains in a sample. Its half life will be:

    A)  2 hour

    B)  3 hour

    C)  6 hour

    D)  12 hour

    Correct Answer: C

    Solution :

     Time of decay t = 1 day = 24 hours Initial amount of the substance \[={{N}_{0}}\] Final amount of the substance \[N=\frac{{{N}_{0}}}{16}\] The relation for the number of half lives is given by \[n=\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{n}}\] \[\left( \frac{1}{16} \right)={{\left( \frac{1}{2} \right)}^{n}}\] \[{{\left( \frac{1}{2} \right)}^{4}}={{\left( \frac{1}{2} \right)}^{n}}\] so      \[n=4\] Therefore, half life is \[{{t}_{\frac{1}{2}}}=\frac{t}{n}=\frac{24}{4}=6\]hours


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