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JEE Main & Advanced Sample Paper JEE Main Sample Paper-32

  • question_answer
    After 280 days, the activity of a radioactive sample is 600 dps. The activity reduces to 300 dps after another 140 days. The initial activity of the sample in dps is:

    A) 6000                      

    B)    9000

    C) 3000                      

    D)    24000

    Correct Answer: D

    Solution :

    In 140 days there is reduction in activity from 600 dps to 300 dps. Thus, half-life of radioactive sample is 140 days. And, activity will remain \[\frac{1}{4}th\] of initial activity in 280 days (i.e. two half-lives) Initial activity \[=\text{ }4\times 6000=24000\]days.


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