Point source (radioactive)that emits 100 gamma per second

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Discussion Overview

The discussion revolves around the effects of a metal or foil on the emission of gamma rays from a point source that emits 100 gamma quanta per second. Participants explore how the attenuation coefficient of the material influences the number of gamma rays that pass through, considering concepts from Beer’s law and the nature of gamma interactions.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the number of gamma quanta emitted would decrease when a metal or foil is placed in front of the source, referencing Beer’s law and the attenuation coefficient.
  • Another participant states that the reduction in gamma quanta depends on the attenuation coefficient, specifically whether it is integrated over energy and all processes.
  • There is a suggestion that the number of gamma quanta may not always decrease, as a high-energy gamma can create an electron-positron pair, resulting in additional gamma emissions from annihilation events.
  • Participants express confusion regarding the distinction between intensity and the number of gamma quanta, indicating a need for clarification on these concepts.

Areas of Agreement / Disagreement

Participants generally agree that the attenuation coefficient plays a crucial role in determining the number of gamma quanta that pass through a material. However, there is disagreement regarding whether the number of emitted gamma quanta always decreases, as some scenarios may lead to an increase in gamma emissions.

Contextual Notes

Participants mention the need for clarity on the definition and application of the attenuation coefficient, as well as the conditions under which it is applied. There is also an acknowledgment of the complexity involved in calculating the effects of gamma interactions with materials.

Rajini
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Hi all,
i have a critical question.
You have a point source (radioactive)..that emits 100 gamma per second. Now if you place a metal or foil (e.g., Al)..will the no. of gamma reduces? If it reduces how to calculate..based on beer law..(if we know the attenuation coefficient of that metal and the energy of that 100 gamma)..sometimes i get confused with intensity and number of gamma quanta.
thanks for your reply
 
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it depends on the attenuation coefficient, if it is the total (i.e integrated over energy and all processes (pairproduction etc))
 


so no. of gamma quanta would decrease depending on the attenuation coefficient?
thanks
 


Rajini said:
so no. of gamma quanta would decrease depending on the attenuation coefficient?
thanks

depends on if you have integrated atten coeff over energy etc
 


There are situations where a single high energy gamma from a radioactive source creates an electron positron pair, which in turn produces two annihilation gammas. So no, the attenuation does not always reduce the number of gammas. angstar is right, the attenuation coefficient can either apply either to the incident photon only, or to any photon of any energy coming out of the attenuator.
Bob S
 


okay..something with exposure rate!..
 

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