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


by what_are_electrons
Tags: electron, mass, measure, mev or cc, units
what_are_electrons
#1
Aug30-04, 02:38 AM
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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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arivero
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#2
Aug30-04, 04:01 AM
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You can give some credit to nuclear beta decay.
colinr
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#3
Aug30-04, 06:23 AM
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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

what_are_electrons
#4
Aug30-04, 10:10 AM
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How do they measure the mass of the electron in units of MeV/c*c ?


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!
Nereid
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#5
Aug30-04, 11:19 AM
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Observations of the energy/wavelength/frequency of the gammas which result from the annihilation of electrons and positrons?
Tom Mattson
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#6
Aug30-04, 11:24 AM
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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.
PatrickRowe
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#7
May11-11, 01:21 PM
P: 4
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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