CET Karnataka Engineering CET - Karnataka Engineering 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 \[={{N}_{0}}\] No 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                                 \[{{t}_{\frac{1}{2}}}=\frac{t}{n}=\frac{24}{4}=6\,\text{hours}\]


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