Question: how do microscopes work?

Ian Hands-Portman answered on 13 Mar 2014:

That’s a big one! and I’ll struggle not to use jargon.
No matter what the basic technology all microscope concentrate some sort of illumination – visible light or electrons for my machines onto a very small spot on a sample and then expand that spot using lenses until it’s much bigger so we can look at it.

In a light microscope like my confocal microscopes the lenses are made of glass just like a magnifying glass but you put several of them in a row to get very high magnifications. A confocal actually sends a laser beam down in the same direction you look, that laser makes a fluorescent dye glow ( like a highlighter pen ) and specials filters block out the laser light coming back so all you can see is the glow of the dye.

The electron microscopes don’t use light, they use electrons which have a much smaller wavelength than light and can see much smaller things. The beam of electrons is blasted through the sample and instead of glass lenses we use huge electromagnets to focus the electron beam. The old way to see the picture was to use something like luminous paint on a metal screen that glowed green when electrons hit it. These days we use camera chips like the ones in a digital camera but quite a lot bigger to record the picture for us.

Feel free to ask more – the question you’ve asked would cover someone’s whole degree!