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

  • question_answer
    The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant                      [DPMT 2003]

    A)            40 year, 0.9173/year         

    B)            90 year, 9.017/year

    C)            80 year, 0.0173 year          

    D)            None of these

    Correct Answer: C

    Solution :

                       To reduce one fourth it takes time \[t=2\left( {{T}_{1/2}} \right)\]= 2 ´ 40 = 80 years.                      Decay constant \[\lambda =\frac{0.693}{{{T}_{1/2}}}=\frac{0.693}{40}=0.0173\,years\]


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