JEE Main & Advanced Sample Paper JEE Main - Mock Test - 28

  • question_answer
    The intensity of gamma radiation from a given source is I. On passing through 36 mm of lead, it is reduced to \[\frac{1}{8}\]. The thickness of lead which will reduce the intensity to \[\frac{1}{2}\] will be

    A) 18 mm             

    B) 12 mm  

    C) 6 mm               

    D) 9 mm

    Correct Answer: B

    Solution :

    \[\operatorname{I}'=I{{e}^{-\,\mu x}}\,\,\,\Rightarrow \,\,x=\frac{1}{\mu }\,\,lo{{g}_{e}}\frac{I}{I'}\] (where \[\operatorname{I} = original intensity\], \[\operatorname{I}' = changed intensity\]) \[36=\frac{1}{\mu }{{\log }_{e}}\frac{I}{I/8}=\frac{3}{\mu }{{\log }_{e}}2\]                 ? (i) \[x=\frac{1}{\mu }{{\log }_{e}}\frac{I}{I/2}=\frac{1}{\mu }{{\log }_{e}}2\] From equation (i) and (ii), \[\operatorname{x} = 12\,\,mm.\]


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