How do they measure the mass of the electron in units of MeV/c*c ?

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Discussion Overview

The discussion centers around the methods used to measure the mass of the electron in units of MeV/c², exploring both historical and modern experimental techniques. Participants express interest in understanding the contemporary approaches beyond classical methods like Millikan's oil drop experiment and Thomson's charge-to-mass ratios.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about modern experimental systems used to determine the electron's mass of 0.511 MeV/c², seeking alternatives to historical methods.
  • Another participant suggests that nuclear beta decay could be relevant to the measurement of the electron's mass.
  • A different participant explains the relationship between mass and energy using the equation E=mc², indicating that mass can be expressed in eV/c² by rearranging the equation.
  • One participant expresses a desire for specific references or links to experimental setups that measure the electron's mass directly in MeV/c².
  • Another participant mentions the observation of gamma rays resulting from electron-positron annihilation as a potential method for measuring mass.
  • One participant argues that there is no unique experimental method for measuring mass in a specific system of units, stating that any measured value can be converted to MeV/c².
  • A later reply raises confusion about converting the mass of a proton into MeV/c² and questions whether this representation reflects the relativistic energy of the particle.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding regarding the measurement of mass in MeV/c², with some proposing methods while others challenge the clarity of unit conversion and measurement techniques. No consensus is reached on a specific modern experimental method.

Contextual Notes

Participants note the dependence on the definitions of mass and energy in different units, as well as the potential for confusion in converting between systems of measurement. The discussion does not resolve the complexities involved in these conversions.

what_are_electrons
What is the experimental system used to determine that an electron has a mass of 0.511 MeV/c*c ?

I'd like to learn about methods other than Millikan's oil drop and Thomson's charge/mass ratios. What is the modern way to generate a value with those units?
 
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You can give some credit to nuclear beta decay.
 
The units come from the equation E =mc^2

If you re-rewite the equation in terms of units eV = kg c^2 and re-arrange it for mass, you get kg = eV/c^2

and so the numerical value for the mass of the electron is equal to the numerical value of its energy/c^2. So we can give mass in terms of eV/c^2
 
I understand what you are saying, but I believe that there is some sort of experimental equipment setup that can and has been used to physically measure the 0.511 MeV or 0.511 MeV/c2 values. It is that info I am after. I would be grateful for any references or links that reveal the nature of that experimental equipment.
Thanks!
 
Observations of the energy/wavelength/frequency of the gammas which result from the annihilation of electrons and positrons?
 
There is no experimental method to single out any system of units. It doesn't matter if you report the measured value of the mass in kilograms, slugs, or dynes/g. You can always convert to MeV/c2.
 
Hello! I'm also confused regarding these units, given the equation E=[tex]\gamma[/tex]mc2, i am to show the mass of a proton in the units MeV/C^2, however i have no idea how to convert into these units. Is this form of the display of mass actually a measure of the relativistic energy that the particle has?
 

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