JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank Mock Test - Modern Physics

  • question_answer
    The rate of disintegration was observed to be 1017 disintegrations per sec when its half-life period is 1445 years. The original number of particles are

    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 :

    [b] Rate of disintegration \[\frac{dN}{dt}={{10}^{17}}{{s}^{-1}}\] Half-life \[{{T}_{1/2}}=1445\]year \[=1445\times 365\times 24\times 60\times 60=4.55\times {{10}^{10}}\sec \]Now decay constant \[\lambda =\frac{0.693}{{{T}_{1/2}}}=\frac{0.93}{4.55\times {{10}^{10}}}=1.5\times {{10}^{-11}}\]Per sec The rate of disintegration \[\frac{dN}{dt}=\lambda \times {{N}_{0}}\Rightarrow {{10}^{17}}=1.5\times {{10}^{-11}}\times {{N}_{0}}\] \[\Rightarrow {{N}_{0}}=6.6\times {{10}^{27}}\]


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