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

  • question_answer
    The rate of disintegration was observed to be \[{{10}^{17}}\] disintegrations per sec when its half life period is 1445 years. The original number of particles are                   [Pb. PET 2001]

    A)            \[8.9\times {{10}^{27}}\]

    B)            \[6.6\times {{10}^{27}}\]

    C)            \[1.4\times {{10}^{16}}\]

    D)            \[1.2\times {{10}^{17}}\]

    Correct Answer: B

    Solution :

               Rate of disintegration \[\frac{dN}{dt}={{10}^{17}}{{s}^{-1}}\] Half life \[{{T}_{1/2}}=1445\] year = 1445 ´ 365 ´ 24 ´ 60 ´60 = 4.55 ´ 1010 sec Now decay constant \[\lambda =\frac{0.693}{{{T}_{1/2}}}=\frac{0.693}{4.55\times {{10}^{10}}}=1.5\times {{10}^{-11}}\] per sec The rate of disintegration \[\frac{dN}{dt}=\lambda \times {{N}_{0}}\Rightarrow {{10}^{17}}=1.5\times {{10}^{-11}}\times {{N}_{0}}\] Þ N0 = 6.6 ´ 1027.27


You need to login to perform this action.
You will be redirected in 3 sec spinner