Pound-Rebka Experiment: Understanding Gamma Ray Detection & Doppler Effect

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Discussion Overview

The discussion revolves around the Pound-Rebka experiment, focusing on the gamma ray detection and the Doppler effect. Participants explore the mechanics of the experiment, particularly the movement of the gamma ray detector and the implications of gravitational blueshift and Doppler redshift.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the gamma ray detector was moving and suggests that the Doppler effect could be used to cancel out the gravitational blueshift.
  • Another participant agrees with the initial inquiry and mentions that the experimenters moved the receiver to offset the gravitational frequency shift with a Doppler shift.
  • A participant reiterates the idea of using the Doppler effect to measure the shift after moving the detector at the right speed to cancel the blueshift.
  • There is a proposal to use the Zeeman effect to measure the shift, suggesting that an atom in a magnetic field could be tuned to absorb the shifted photon that would otherwise not be detectable due to redshift.
  • One participant expresses confidence that the proposed method involving the Zeeman effect should work.

Areas of Agreement / Disagreement

Participants generally agree on the basic mechanics of the Pound-Rebka experiment and the use of Doppler effects, but there are varying opinions on the feasibility of using the Zeeman effect for measurement, indicating some uncertainty and exploration of different approaches.

Contextual Notes

Some assumptions about the movement of the detector and the specifics of the Doppler effect application remain unaddressed, and the discussion does not resolve the potential effectiveness of the proposed Zeeman effect method.

cragar
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Im trying to understand the pound- rebka test , so was the gamma ray detector moving
, when the photon gets shot from the top of the 4th floor of the science building at harvard
to the bottom it will be blue shifted , so would they want to move the detector away at a certain speed so the doppler effect will cancel out the blueshift , and the speed that the detector is moving then using the doppler effect equation we could calculate the shift.
Any input will be much appreciated.
 
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Yes, I think you're on the right track although it's hard to follow what you've written. This Wiki entry might explain ( if you have not seen it already ). The experimenters certainly moved the receiver to offset the gravitational frequency shift with a Doppler shift.

http://en.wikipedia.org/wiki/Pound–Rebka_experiment
 
cragar said:
Im trying to understand the pound- rebka test , so was the gamma ray detector moving
, when the photon gets shot from the top of the 4th floor of the science building at harvard
to the bottom it will be blue shifted , so would they want to move the detector away at a certain speed so the doppler effect will cancel out the blueshift , and the speed that the detector is moving then using the doppler effect equation we could calculate the shift.
Any input will be much appreciated.

The reason is that once you move the detector at the right speed, the experimenters managed to cancel out the gravitational blueshift through the relativistic Doppler redshift. The idea was that the Doppler redshift was used as an easy to measure effect (through measuring the elevator speed "v").
 
ok so the detector was moving towards the Earth in an elevator with a speed V .
And i am just wondering could we use the zee man effect to measure the shift ,
could we use an atom that had a specific wavelength of a photon between the ground state and some other state , that could be absorbed from the emitter but could not be absorbed at the detector because of the red shift , but if we placed the atom's in a magnetic field at the detector and had the strength of the B field tuned precisely to accept the shifted photon , would this work.
 
cragar said:
ok so the detector was moving towards the Earth in an elevator with a speed V .
And i am just wondering could we use the zee man effect to measure the shift ,
could we use an atom that had a specific wavelength of a photon between the ground state and some other state , that could be absorbed from the emitter but could not be absorbed at the detector because of the red shift , but if we placed the atom's in a magnetic field at the detector and had the strength of the B field tuned precisely to accept the shifted photon , would this work.

yes, should work
 
sweet thanks for your response .
 

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