Manipal Medical Manipal Medical Solved Paper-2013

  • question_answer
    Half-life of radium is 1600 yr. If the initial mass is 1 kg, what is the amount of radium left after 4800 yr?

    A)  Zero                 

    B)  0.125 kg

    C)  0.5 kg                

    D)  0.25 kg

    Correct Answer: B

    Solution :

     From Rutherford and Soddy law for radioactive decay, if N be the number of atoms of radioactive substance lift at some instant of time, then \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\] When\[{{N}_{0}}\]is original number of atoms and\[n\]is number of half views Given, \[{{T}_{1}}/2=1600yr,{{N}_{0}}=1\,kg\] \[n=\frac{4800}{1600}=3\] \[N={{\left( \frac{1}{2} \right)}^{3}}\times 1\] \[=\frac{1}{8}=0.125\,kg\]


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