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

In summary, the modern method for determining the mass of an electron in units of MeV/c^2 involves using the equation E=mc^2 and rearranging it to solve for mass in terms of energy and the speed of light. This can be done through observations of the energy and wavelength of gammas resulting from electron-positron annihilation. It doesn't matter which system of units is used to report the mass, as it can always be converted to MeV/c^2.
  • #1
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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  • #2
You can give some credit to nuclear beta decay.
 
  • #3
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
 
  • #4
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!
 
  • #5
Observations of the energy/wavelength/frequency of the gammas which result from the annihilation of electrons and positrons?
 
  • #6
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.
 
  • #7
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?
 

1. How is the mass of the electron measured in units of MeV/c*c?

The mass of the electron is measured using a technique called mass spectroscopy. This involves accelerating electrons through an electric or magnetic field and measuring their deflection. By comparing the deflection of electrons to that of known particles with a known mass, the mass of the electron can be determined.

2. What are MeV and c*c in the unit of measurement for the mass of the electron?

MeV stands for Mega-electron volts, which is a unit of energy commonly used in particle physics. It is equivalent to 1.6 x 10^-13 Joules. c*c refers to the speed of light squared, which is a constant in Einstein's famous equation E=mc^2. It is equal to approximately 9 x 10^16 meters squared per second squared.

3. Why is the mass of the electron measured in MeV/c*c?

The mass of the electron is measured in units of MeV/c*c because it is a more convenient unit for expressing the extremely small mass of the electron. Using this unit allows for easier comparison and calculation of the mass of the electron with other particles.

4. How accurate is the measurement of the mass of the electron in units of MeV/c*c?

The current accepted value for the mass of the electron in units of MeV/c*c is 0.511 MeV/c*c with an uncertainty of 0.000015 MeV/c*c. This means that the measurement is accurate to within 0.003%. However, as technology and measurement techniques improve, this accuracy is expected to improve as well.

5. What is the significance of measuring the mass of the electron in units of MeV/c*c?

The mass of the electron is a fundamental constant in physics and is used in various calculations and equations. By measuring it in units of MeV/c*c, we can better understand the behavior and interactions of particles at the subatomic level. It also allows for better comparison and study of other particles with similar masses, such as the muon and tau particles.

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