Help Solving Physics Exam Question on Gamma Rays Counting Rate

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Discussion Overview

The discussion revolves around a physics exam question regarding the counting rate of gamma rays emitted by a radioactive source. Participants explore the statistical concepts involved in determining the error in the counting rate based on recorded counts over a specific time interval.

Discussion Character

  • Exploratory, Technical explanation, Homework-related

Main Points Raised

  • One participant seeks clarification on the concept involved in calculating the error in the counting rate of gamma rays.
  • Another participant questions the statistical distribution that describes the number of counts in the given time frame.
  • A participant asserts that the problem likely involves the Poisson distribution, which is commonly used for counting events in fixed intervals.
  • It is proposed that the error in the counting rate per second can be calculated as the square root of the counts recorded, leading to a specific numerical result.

Areas of Agreement / Disagreement

Participants generally agree on the use of the Poisson distribution for this type of problem, but there is no consensus on the details of the statistical concepts or the specific calculations involved.

Contextual Notes

The discussion does not clarify the assumptions regarding the statistical distribution or the context in which the counting error is applied. There is also no resolution on the exact nature of the reading materials referenced.

Who May Find This Useful

Students preparing for physics exams, particularly those focusing on statistical methods in experimental physics.

DM107
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Hi,

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?
 
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What is the statistical distribution which describes the number of counts in 20 s?
 
No distribution was given with the question Dale.
 
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?
 
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!
 
Good job!
 
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