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JEE Main & Advanced Sample Paper JEE Main Sample Paper-40

  • question_answer
    The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second at t = 6 seconds will be

    A) 400                             

    B) 300

    C) 200                             

    D) 150

    Correct Answer: C

    Solution :

    After 8 sec., the counting rate falls to \[\frac{100}{1600}=\frac{1}{16}={{\left( \frac{1}{2} \right)}^{4}}\]th Part; Time period \[=\frac{8}{4}\sec .=2\sec .\] "Therefore, after 6 seconds, the counting rate should be \[{{\left( \frac{1}{2} \right)}^{3}}\] th part of 1600, i.e. \[\frac{1}{8}\times 1600=200.\]


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