Radioactive decay characteristics as measured by a dosimeter

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Discussion Overview

The discussion revolves around the characteristics of radioactive decay as measured by a dosimeter, specifically focusing on how the dose level received by the dosimeter changes over time as a gamma sample decays. Participants explore the relationship between the decay rate, dose rate, and the concept of half-life, with an emphasis on whether the decrease in dose level is linear or exponential within the half-life period.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the dose level received by the dosimeter would gradually decrease over the first half-life or remain constant until the end of that period.
  • Another participant asserts that the decrease of dose level would be gradual and continuous.
  • A reference to a graph illustrating exponential decay is made, suggesting that the decay rate is proportional to the remaining amount at any given time.
  • One participant clarifies that while the accumulated dose will always increase, the rate of dose will decrease exponentially.
  • A participant expresses a desire to understand how the dose decreases specifically within one half-life, questioning whether it is linear or exponential during that time frame.
  • There is a correction regarding terminology, emphasizing the distinction between "dose" and "dose rate," with a claim that the dose rate decreases exponentially at all times.
  • A follow-up question is posed regarding the graph, asking for clarification on any observed transition between linear and exponential decay within the half-life period.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the nature of the decay within the half-life period, with some suggesting a gradual decrease and others emphasizing the exponential nature of the decay rate. The discussion remains unresolved as participants explore different interpretations and clarifications.

Contextual Notes

There are limitations in the discussion regarding the definitions of "dose" and "dose rate," as well as the assumptions made about the decay characteristics within the half-life period. The relationship between the graphical representation of decay and real-time measurements is also not fully resolved.

artis
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If I put a dosimeter 1 meter away from a gamma sample that starts decaying at the moment I switch on the dosimeter then how would I measure the dose level received by the dosimeter, would it gradually decrease over the first half life or would it stay the same throughout the first half life until the end of the half life?

I ask this because I know isotopes have a exponential rate at which they decay , as in the majority of atoms can decay within the first part or the last part of the half life but how does that translate into actual levels seen by dosimeter?
 
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artis said:
If I put a dosimeter 1 meter away from a gamma sample that starts decaying at the moment I switch on the dosimeter then how would I measure the dose level received by the dosimeter, would it gradually decrease over the first half life or would it stay the same throughout the first half life until the end of the half life?

I ask this because I know isotopes have a exponential rate at which they decay

The decrease of dose level would be gradual and continuous.
 
See the graph at the top of this page: https://en.wikipedia.org/wiki/Exponential_decay

It shows the amount remaining undecayed as time passes. The decay rate (number of decays per second) follows a similar curve because it's proportional to the remaining amount at every point in time.
 
Let's be careful here. The dose is integrated so will always increase. The rate of dose will decrease exponentially.
 
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Well I was thinking in terms of real time radiation strength received by dosimeter rather than an accumulated dose of a person over a time interval.
I understand the dose decreases exponentially as it halves after each half life so 1/4 is left after the second half life but I was wondering how it decreases specifically within the margin of one half life, more linearly or also exponentially ?jtbell the graph you referred to, does it mean that the first half lifes decay almost linearly within the margin of half life itself and the later ones decay more exponentially within the same margin of that half life?
 
Don't call it dose if you mean the dose rate. That's like taking about the maximal distance of car if you mean the top speed.
artis said:
more linearly or also exponentially ?
The dose rate decreases exponentially. That is a general statement that applies to all times. There is nothing special about the half-life time.
 
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artis said:
jtbell the graph you referred to, does it mean that the first half lifes decay almost linearly within the margin of half life itself and the later ones decay more exponentially within the same margin of that half life?
For which curve in that graph do you see a transition between linear and exponential, and at what time?
 

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