So, I'm told that electron microscopy provides greater resolution than traditional photo/optical (i.e. visible light) microscopy, due to the (ahem) "fact" that "electrons are physically smaller than photons".. Which I'm pretty sure is not necessarily true, (or static/constant). But by the same token, I am not a physicist..

The analogy that I'm presented with is that in this context, the size (and density) of photons and/or electrons are supposedly comparable to pixels (and ppi/dpi) of an LCD monitor, CCD image sensor, raster image, etc.

So, it sounds plausible, and it's a nice, relatable explanation for the common man. But is it factual? If not, what's really going on here?

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    $\begingroup$ The wavelength is shorter, yes. $\endgroup$
    – Jon Custer
    Jun 7 '18 at 1:39
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    $\begingroup$ Visible light wavelengths are ~500-700 nm. A typical atom is ~0.1-0.2 nm. An electron is much smaller than an atom. $\endgroup$
    – The Photon
    Jun 7 '18 at 2:08
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    $\begingroup$ Elementary particles don't have size. If anyone tells you that "electrons are smaller than photons", run away and never listen to him again. $\endgroup$
    – safesphere
    Jun 7 '18 at 4:21
  • $\begingroup$ Protons have a measurable size. $\endgroup$
    – my2cts
    Jun 7 '18 at 10:16

Here is a basic overview- experts are invited to add detail.

Subatomic particles like electrons actually possess a wavelength that is related to their energy, even though they behave most of the time like tiny point particles and not like waves. By accelerating a beam of electrons to very high energies, their wavelengths become far shorter than that of a photon of visible light, and this allows them to resolve objects far smaller than that which can be seen with focused beams of visible light.

In a typical electron microscope, the electron beam tube in which the acceleration occurs is about three to four feet long, but this principle can be scaled up to resolve the interior of a single proton. In this case, the beam tube needs to be more than ten thousand feet long; the SLAC particle accelerator in California has one of these 2.2 miles long which was used to detect the interior structure of protons in the late 1960's.

  • $\begingroup$ Can you please tell me why we are using electrons, instead of using non-visible light waves, that have the same short wavelength? $\endgroup$ Jun 7 '18 at 5:27
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    $\begingroup$ Because it is very easy to build lenses that focus electron beams, using magnets and electrostatic plates. it is very difficult to build lenses to focus photons with wavelengths shorter than soft UV (which was actually used in some microscopes prior to the invention of electron microscopy), because shorter than that you get X-rays which cannot be lensed except by near-grazing incidence reflection. $\endgroup$ Jun 7 '18 at 5:45
  • $\begingroup$ @ÁrpádSzendrei - X-ray optics. $\endgroup$
    – Rob
    Jun 7 '18 at 6:22
  • $\begingroup$ Or multilayer mirrors. $\endgroup$
    – my2cts
    Jun 7 '18 at 10:13

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