According to Wikipedia, “An electron microscope is a microscope that uses a beam of accelerated **electrons** **as a source of illumination**. **As the wavelength of an electron can be up to 100,000 times shorter than that of visible light** **photons**, **electron microscopes have a higher resolving power** **than** **light microscopes** **and can reveal the structure of smaller objects**”.
Can anyone explain the text in bold? I don’t understand how an electron can be a source of illumination.
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The electrons bounce off the object. The way they bounce reveals the structure of the object. This is exactly how light illuminates something, too: the photons bounce off it, and how they bounce and which photons bounce tells you about the object.
(Strictly speaking this is a *scanning* electron microscope. Others, like TEMs, work differently. But the basic principle – that you use how electrons interact with the material to probe its structure – remains.)
The reason you can’t use light at these scales is that (visible) light is “too big” to bounce off small details. If I put an object on a pool table and asked you to figure out its shape by bouncing marbles off it, you could do it. But if I asked you to figure out its shape using giant beach balls, you’d have a much harder time. In this analogy, electrons are like marbles, and photons of visible light are like the beach ball.
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