NEET Sample Paper NEET Sample Test Paper-21

  • question_answer
    Plutonium has atomic mass 210 and a decay constant equal to \[5.8\times {{10}^{-8}}{{\sec }^{-1}}.\] The number of a-particles emitted per second by 1 mg is: (Avogadro's constant\[=6.0\times {{10}^{-23}}\])

    A) \[1.7\times {{10}^{9}}\]      

    B)   \[1.7\times {{10}^{11}}\]    

    C)   \[2.9\times {{10}^{11}}\]    

    D)   \[3.4\times {{10}^{9}}\]   

    Correct Answer: B

    Solution :

    No. of \[\alpha -\]particles per second \[=A=-\frac{dN}{dt}=N\lambda \]is required where \[N=\frac{6.0\times {{10}^{-23}}}{210}\times 1\times {{10}^{-3}}\]and \[\lambda =5.8\times {{10}^{-8}}\]per second So, \[A=N\lambda =\frac{6.0\times {{10}^{-23}}}{210}\times 1\times {{10}^{-3}}\times 5.8\times {{10}^{-8}}\]             \[\approx 1.7\times {{10}^{11}}\] Hence, the correction option is (b).

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