Why can we not see electrons or any other subatomic particle with our naked eye, without using any apparatus?
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$\begingroup$ With a little help you could see them en.wikipedia.org/wiki/Cloud_chamber .. Take a look at this tutorial from ESA (maybe you can build your own detector) esa.int/Education/Teachers_Corner/… $\endgroup$– Mihai B.Commented Mar 18, 2017 at 7:51
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$\begingroup$ And sometimes energetic electrons can get into the nerves that connect your eyes and the brain and you can get to see something like this, very much analogues to the cloud chamber physics.stackexchange.com/questions/312064/… $\endgroup$– Mihai B.Commented Mar 18, 2017 at 7:53
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$\begingroup$ You can not see them otherwise. They would need to emit light all the time but that would mean that electrons are big enough to reflect light (all the time) and not alter their path each time. But electrons and visible light rays interaction is kind'a dramatic when it comes to electron's path. Etc ... $\endgroup$– Mihai B.Commented Mar 18, 2017 at 7:57
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How do we see objects? We 'see' objects when light reflects off them and reaches our eyes. Theres a fact that light cannot reflect off objects smaller than half the wavelength of the light used. Smallest wavelength of light is for violet, which is 400nm, half of it is 200nm. The classical radius of an electron is 2.817*10^-15m (Wikipedia source), which is much smaller than the wavelength of light. Since light wont reflect off an electron, you cant see it.
answered Mar 18, 2017 at 7:59
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$\begingroup$ Thanks for your explanation. But how was it discovered? $\endgroup$– HiggsCommented Mar 18, 2017 at 10:12
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$\begingroup$ +Higgs I wish I knew why, but sorry, I dont :) $\endgroup$ Commented Mar 18, 2017 at 13:31
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3$\begingroup$ @PrittBalagopal how was what discovered? the size of an electron? it is an upper limit from various experiments example S. Brodsky and S.D. Drell, Anomalous magnetic moment and limits on fermion substructure, Phys. Rev. D 22 (1980), pp. 2236-2243. $\endgroup$– anna vCommented Mar 18, 2017 at 14:24