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Electrons are massless ?

  1. Nov 10, 2005 #1
    Electrons are "massless"?

    Why are electrons described as "massless". It seems to me that they would have to have mass. Are they truly massless or is this the same kind of aproximation that is made with ideal gas laws?
  2. jcsd
  3. Nov 10, 2005 #2


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    An electron is a lepton with rest mass of 0.511 MeV (or 9.11 x 10-31 kg).

    Compared to a proton of rest mass 938.27 MeV (1.6726231 x 10-27 kg), the electron is light, but not massless.

    Perhaps the article cited by ZapperZ indicates that electrons in certain conditions behaves as massless particles.

    From the article on PhysicsWeb -
    Further investigation has revealed
    Go to Zz's thread https://www.physicsforums.com/showthread.php?t=99223
    Last edited: Nov 10, 2005
  4. Nov 10, 2005 #3
    well, my chem teacher calls them masssless, which annoys me, which is why asked.
  5. Nov 10, 2005 #4


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    Chemistry people are nuts :P

    Is this high school? College professors wouldn't make such a mistake....
  6. Nov 10, 2005 #5
    ya its HS. Cool guy, really good teacher , I think he just doesn't want to confuse the rest of the class when were doing atomic mass. At least, I'm assuming that what is was.
  7. Nov 10, 2005 #6


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    Yah that is probably the reason. When i was in high school, i was like "wait wait wait, you didn't add in the electrons :(". He still shouldn't say they are massless however, he should just say they are too small to be considered in weighing masses at a high school level.
  8. Nov 10, 2005 #7
    he might have said they were negligible once.
    While i'm on the topic- gamma rays (edit:particles not rays) have mass- correct?
    Cause he did say that those were massless.
  9. Nov 11, 2005 #8


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    There is no such thing as a gamma particle. Gamma rays are massless however.
  10. Nov 11, 2005 #9
    ok, maybe it is gamma rays I am thinking of then, we were doing radiation, he was talking about it like it was a particle, but then he called it a ray, left me kinda confused.
  11. Nov 11, 2005 #10


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    Well it's an electromagnetic wave as far as i know :)
  12. Nov 11, 2005 #11
    about gamma-rays... They shouldn't be the electromagnetic waves with the most corpuscular behaviour? The great deal of particle aspect of light (i.e. see Compton effect: a photon come to act like a ball that on a pool table matches another one, the electron, which is a really material particle despite gamma-ray!) is to attribute to them!
    It is a strange dualism, for which some people have never come out!

    Sorry for my spit-joint english

  13. Nov 12, 2005 #12


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    Well, there's alpha particles, beta particles, and gamma particles/rays. Gamma rays, are photons, electromagnetic radiation. Wave-particle duality. And photons kind of have mass and kind of don't... rest mass they do have.
  14. Nov 12, 2005 #13


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    Whoa! Since when?

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