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Detector error

  1. Nov 23, 2014 #1

    I came across a question in an exam which I couldn't really relate to any topic of physics, that I had studied.
    It goes like this-

    A detector is used to count the number of gamma rays emitted by a radioactive source. If the number of counts recorded in exactly 20 seconds is 10000, the error in the counting rate per second is?

    Can someone please let me know what concept is involved so that I can try and solve it?
  2. jcsd
  3. Nov 23, 2014 #2


    Staff: Mentor

    What is the statistical distribution which describes the number of counts in 20 s?
  4. Nov 23, 2014 #3
    No distribution was given with the question Dale.
  5. Nov 23, 2014 #4


    Staff: Mentor

    The distribution for this kind of problem won't be given in the question itself. It is well known and would certainly have been covered extensively in the reading.

    Which distributions were covered in the reading, and what do those distributions describe?
  6. Nov 23, 2014 #5
    I got it Dale. Its poisson distribution.
    and the error in counting rate per second will be sqroot(500) which is 22.4.

    Thanks a lot!
  7. Nov 23, 2014 #6


    Staff: Mentor

    Good job!
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