How do electron microscopes work?
In: Planetary Science
A light microscope shines photons (which have a relatively long wavelength, relative to EM scopes) at whatever you’re trying to see in higher detail, they bounce off, hit a detector (your retina or a digital sensor) and you get an image.
The wavelength of whatever you’re shooting at your sample (in this case, visible light) limits the resolution, higher wavelength = lower resolution, for complicated physics/optics reasons I’m not able to explain off the top of my head. There is a limit to how close two points can be before they look like one point, through any kind of microscope, and it depends on the wavelength of your “illumination” source.
The wavelength of visible light is in the hundreds of nm (nanometers), but for electrons, it’s .003 nanometers. Which increases resolution tremendously. So in EM, instead of shining a beam of visible light, you shine a beam of electrons. And then capture the image using a different type of sensor, with the image eventually converted to something we can see with our eyes. (Which will, incidentally, kill living things, because electron beams are very high energy, which limits what you can image. No EM microscopy of live bacteria, for example.)
However, electrons can pass right through a lot of things without reflecting, so you have two kinds of electron microscopy, TEM (transmission EM) and SEM (scanning EM), with the latter requiring that you treat (coat, actually) the sample in special ways that will reflect the electrons.
The really neat images of ants showing insane detail are SEM [https://en.m.wikipedia.org/wiki/File:Ant_SEM.jpg](https://en.m.wikipedia.org/wiki/File:Ant_SEM.jpg), the grainy ones showing mitochondria as fuzzy objects are TEM. [https://upload.wikimedia.org/wikipedia/commons/0/0c/Mitochondria%2C_mammalian_lung_-_TEM.jpg](https://upload.wikimedia.org/wikipedia/commons/0/0c/Mitochondria%2C_mammalian_lung_-_TEM.jpg)
The “ugly” ones are actually much higher mag, but they only show you a “slice” of what you’re imaging.
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