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  3. CEE Kerala Engineering

CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2005

  • question_answer
    The counting rate observed from a radioactive source ate = 0 s was 1600 count/s and at\[t=8\]s it was 100 counts/s. The counting rate observed as counts per second at\[t=6\text{ }s,\]will be:

    A)  400                       

    B)         300

    C)  250                       

    D)         200

    E)  150

    Correct Answer: D

    Solution :

    The half-life of source\[=\frac{8}{4}=2s\] Now,       \[R={{R}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\]                 \[R=1600{{\left( \frac{1}{2} \right)}^{\frac{6}{2}}}\]                 \[=1600{{\left( \frac{1}{2} \right)}^{3}}\]                 \[=200\]


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