Why do electron microscopes have better resolution than light microscopes, when electrons are much bigger than photons?

http://bsp.med.harvard.edu/node/222

In light microscopy, visible light (photons) is transmitted through or reflected from a sample and then passed through optical lenses to achieve magnification. The major limitation of standard optical microscopy lies in the diffraction limit of resolution (first approximated by Ernst Abbe). (Diffraction is a phenomenon whereby a beam of light or other system of waves is spread out as a result of passing through a narrow aperture, typically accompanied by interference between the wave forms produced.) This limit can be calculated to be approximately 0.2 µm (it is distance that depends on the wavelength of light; see Fig. 2 below). Another limitation is out of focus light from outside the focal plane reducing image clarity. On the other hand, under the right conditions, light microscopy allows for imaging of samples that are alive. In addition, using flourescent proteins, fluorescence light microscopy can be used to track proteins in real-time in cells (though at limited spatial resolution; ie. you may see roughly where the protein is in the cell, but will not be able to see the shape of the protein itself). Meanwhile, confocal light microscopy gives moderately higher resolution, and significant enhancements in optical sectioning by limiting out-of-focus light.

In electron microscopy, on the other hand, a beam of electrons (stable subatomic particles with a negative charge, which orbit positively charged nuclei of atoms) instead of light (or photons) is sent through a very thin slice of the specimen (in the case of Transmission electron microscopy; TEM). Because the electron beam has a far smaller wavelength than light used in light microscopy, it achieves far better resolution, and the current resolution of limit of the best electron microscope is approximately 0.05 nm (atomic resolution, and 4000X better magnification than that of a conventional light microscope!). What does this mean? This means that with an electron microscope you can potentially achieve enough magnification to observe the shape of the protein machinery that carries out the work inside of cells (see Fig. 3 below, and also: “What can you see with EM?”). However, the major limitation of electron microscopy is that specimen preparation requires the biological sample to be fixed to preserve its structure, before viewing under the microscope. This means that the sample will not be alive; it means that while you can observe the shape of your protein machine, you will not be able to observe it changing its shape and carrying out its work in cells in real-time (which would be a biologist’s dream).

basically it is the wavelength.

OK thanks

Are there any proposed or theoretical methods for achieving better resolution than electron microscopes

Cymek said:

Are there any proposed or theoretical methods for achieving better resolution than electron microscopes

Atomic Force microscope.

https://en.wikipedia.org/wiki/Atomic_force_microscopy

Any progress on the quark microscope?

basically it is the wavelength.

Yep. Wavelength of light is 390 to 700 nm. Small enough for bacteria (typical size 200*2000 nm) but nothing much smaller.
Scanning electron microscopes are limited to about 2 nm. Transmission electron microscopes can image smaller objects, eg. 0.2 nm, but to do that you need to slice your specimen really finely.

Are there any proposed or theoretical methods for achieving better resolution than electron microscopes

Atomic Force microscope. https://en.wikipedia.org/wiki/Atomic_force_microscopy

There are others, too. The scanning tunnelling microscope was invented before the AFM and is almost as good.
“For an STM, good resolution is considered to be 0.1 nm lateral resolution and 0.01 nm depth resolution”.

Any progress on the quark microscope?

On the what?