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RAJASTHAN PMT Rajasthan - PMT Solved Paper-2004

  • question_answer
    The half life of radioactive substance is 4 days. Its 100 g is kept for 16 days. After this period, the amount of substance remained is:

    A)                      25g                                                       

    B)              15 g            

    C)              10 g                      

    D)                                         6.25g

    Correct Answer: D

    Solution :

    \[\frac{M}{{{M}_{0}}}={{\left( \frac{1}{2} \right)}^{t/{{T}_{1/2}}}}\] Here : \[{{M}_{0}}=100g,t=16\]days, \[{{T}_{1/2}}=4\]days From eq (1), we get \[\therefore \]  \[M=100{{\left( \frac{1}{2} \right)}^{16/4}}\]                                    \[=100\times {{\left( \frac{1}{2} \right)}^{4}}=100\times \frac{1}{16}=6.25g\]


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