# How smaller can we see?

1. Aug 23, 2007

### jobyts

using an electron microscope or some instrument of that sort?

Molecular level, atomic level, sub-atomic level?

The whole theory of quarks and stuff like that are developed because
1. We could see/observe the behavior of the quarks through some instruments directly or indirectly
2. or, we could see some properties in a macro level that can not be explained without the help of these particles? (so that someone came up with some convincing theories to explain...)
3. or, pure mathematical proof exists

Last edited: Aug 23, 2007
2. Aug 23, 2007

### mgb_phys

Generally with a microscope you can see roughly the size of the wavelength of whatever you are using. So 500nm (ie virus size) for light microscope, 100nm for UV. With an electron microscope you can micron size structures because of the shorter wvelength of electrons.

It is possible to 'see' individual atoms with an atomic force microscope, this drags a very small needle accross the same and records the force on it to detect individual atoms - wether this is 'seeing' or not is a matter of definition.

You can see subatomic particles by bouncing other particles off them, again if this is seeing is up to you. In physics we make models and predict the effects of those models, we then do experiments to measure those effects - if they match our model we have 'seen' the thing we were looking at.

3. Aug 23, 2007

### chroot

Staff Emeritus
In a very real sense, particle accelerators are just the bigger, badder cousins of the standard tabletop light microscope.

- Warren

4. Aug 23, 2007

### jobyts

Thanks mgb_phys for your response. Is there a place where the public could use these special types of microscopes, like the way they have for giant telescopes? I live in SFO bay area.

5. Aug 23, 2007

### olgranpappy

Maybe... But, sometimes these big nice electron microscopes are pretty expensive and the owners don't like letting just anybody mess around with them (they are also a little more dangerous than telescopes and the sample setup is a bit more work). Perhaps other people know the answer to this question...

Oh, one more suggestion: If you want some hands-on experience with an electron microscope, and you are willing to use a "transmission electron microscope" (TEM) rather than a "atomic-force-whatever electron microscope", you could enroll in a university advanced lab because I am sure that they would have an old Davidson-Germer setup.

...And the Davidson-Germer setup is exactly an old-school TEM--it uses diffraction of electrons (I.e., their scattering off atoms) to determine interatomic distances (I.e., "see" how far apart the atoms of the crystal are).

Or, even if you don't enroll in a class, I'll bet that one of the lab TAs would show you their electron diffraction setup... If you are nice about it (read: Not F-ing Crazy).

6. Aug 26, 2007

### AcidBathSDMF

I go to the University of Missouri - St. Louis and have done some research concerning STEM images (Scanning Transmission Electron Microscope). They were taken at Oak Ridge Nation Labs which have one of the highest resolution STEMs in the world. The resolution in STEMs depend on how small you can get the electron probe, and in this case it's in the sub-Angstrom range (1x10^-10 m, or 1/10 nm). To put this in perspective, we generally think of atoms as having an average diameter of about 2 Angstroms. The image I'll attach (assuming I can figure out how) is of pre-solar carbon with heavy atoms strung throughout. This is what's called a "dark field" image, so the detector is off-axis and records current of electrons that were scattered, i.e. hit something. The pixels that are lit up like stars in the night sky are very likely individual atoms; heavy relative to the carbon.

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