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NEET Sample Paper NEET Sample Test Paper-2

  • question_answer
    A freshly prepared radiactive source half-life 2h emits radiation of intensity which 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source is:

    A)  \[6h\]                

    B)  \[12h\]

    C)  \[42h\]               

    D)  \[128h\]

    Correct Answer: B

    Solution :

    As  \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{t/T}}\] or \[\left( \frac{1}{64} \right)={{\left( \frac{1}{2} \right)}^{t/T}}\] or \[{{\left( \frac{1}{2} \right)}^{6}}={{\left( \frac{1}{2} \right)}^{t/T}}\] or  \[\frac{t}{T}=6\] \[\therefore \]    \[t=6T\]  or  \[t=6\times 2=12h\]


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