JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank Critical Thinking

  • question_answer
    The half life of radium is 1620 years and its atomic weight is 226 kgm per kilomol. The number of atoms that will decay from its 1 gm sample per second will be [MP PMT 1993; BVP 2003]

    A)            \[3.61\times {{10}^{10}}\]      

    B)            \[3.6\times {{10}^{12}}\] 

    C)            \[3.11\times {{10}^{15}}\]      

    D)            \[31.1\times {{10}^{15}}\] (Avogadro's number \[N=6.02\times {{10}^{26}}\]atom/kilomol)

    Correct Answer: A

    Solution :

               \[\frac{dN}{dt}=\lambda N;\] \[\lambda =\frac{0.6931}{{{t}_{12}}}=\frac{0.6931}{1620\times 365\times 24\times 60\times 60},\]                    \[N=\frac{6.023\times {{10}^{23}}}{226}\]                    \[\therefore \frac{dN}{dt}=\frac{0.6931\times 6.023\times {{10}^{23}}}{1620\times 365\times 24\times 60\times 60\times 226}\]\[\frac{1}{2}M{{v}^{2}}=qV.\]


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