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RAJASTHAN ­ PET Rajasthan PET Solved Paper-2006

  • question_answer
    The count rate of Geigez -Muller counter for the radiation of a radioactive material of half life of 30 min decreases to\[5{{s}^{-1}}\]after 2 h the initial count rate was

    A)  \[25{{s}^{-1}}\]           

    B)  \[80{{s}^{-1}}\]

    C)  \[625{{s}^{-1}}\]          

    D)  \[20{{s}^{-1}}\]

    Correct Answer: B

    Solution :

     Given: \[{{t}_{1/2}}=36\text{ }min=1800s\] No. of half year \[n=\frac{2\times 60\times 60}{1800}\] \[n=4\] \[{{A}_{0}}={{(2)}^{n}}.N={{2}^{4}}\times 5\] \[{{A}_{0}}=80{{s}^{-1}}\]


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