I know the machine fires electrons at a sample and the electrons are reflected back. How does that translate into a super detailed image? Why is it higher resolution than a light microscope? Why can it only use dead samples?
Edit: Also, why is it in black and white?
In: Technology
>I know the machine fires electrons at a sample and the electrons are reflected back.
This is close enough for our purposes.
>How does that translate into a super detailed image?
The important item here is that the level of detail you can resolve depends on the wavelength of what you’re bouncing off the target. You can see finer details if you image in blue light (450nm) than Near IR (2000 nm).
Due to quantum physics being weird, electrons aren’t really balls but instead wiggly energy packets that have a wavelength. There are a bunch of different ways to calculate the wavelength of fundamental particles like electrons but in general its <1nm making it able to show you much much finer detail than light could because it can sneak into nooks and crannies.
If you take a microscope and just keep cranking up the zoom on an optical image, it will get bigger but it will also get blurrier because the little distortions from when the light clipped the edge of the lens and tiny abnormalities of the lenses matter when you’re at 1,000,000x zoom. This is the same reason you can’t just zoom wayyyyy in on an 8 inch telescope and see great detail on Pluto, you need a bigger lens and shorter wavelength to let you capture the detail so you can zoom in on it.
Since the electron wavelength is soo much smaller you can zoom in proportionally more before the edge effects matter and blur your image beyond use.
> Why can it only use dead samples?
Because it’d be dead by the time you’re sampling it
What happens when you shoot the electron beam? It smacks into atoms and sends other electrons shooting off to be detected. If you have air in the chamber that air would catch the electrons before they hit your sample so electron microscopes are all in vacuum chambers and suck all the air out before imaging.
The sample is also generally prepped in a fine layer of carbon or gold to give a nice conductive surface for good imaging. That wouldn’t be particularly great for anything that was alive.
>Also, why is it in black and white?
Because you’re better at detecting changes in black/white than in color
All the sensor is getting back is a location on it and how many electrons hit that spot, its effectively only able to judge brightness and can’t tell you anything about those electrons. When you look at a color image its because you want to know the count of how many photons would have triggered your red cones, your green cones, and your blue cones, but if you only have one set of data (photons that hit cones) then grayscale is the right way to represent that
If you need more information about the surface an electron microscope has tools *wayyyy* better than color. You can put down the little cursor and go “hey what’s this?” and the system will shoot electrons at it and plot you [the chemical analysis of that spot](https://www.researchgate.net/profile/Hanan-Youssef-7/publication/272408064/figure/fig3/AS:323999889412099@1454259001358/SEM-and-EDS-chemical-analysis-for-the-Ag-substituted-Ti-Z-A.png) which tells you what its made of and roughly how much of what which is *wayyyyy* better than trying to eyeball the color to tell if its copper or gold
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