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NEET Sample Paper NEET Sample Test Paper-4

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

    A)  \[6h\]                          

    B)  \[12\,h\]

    C)  \[42\,h\]                      

    D)  \[128\,h\]

    Correct Answer: B

    Solution :

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


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