How Everything Works
How Everything Works How Everything Works

Question 455

Can (or has) the nucleus be seen through microscopes?
Not exactly. A microscope "sees" an object by sending waves at that object and then looking at the waves it reflects or transmits. For example, a common light microscope sends light waves at an object and allows you to observe the transmitted or reflected light.

Unfortunately, light waves can't resolve details smaller than about 1/2 their wavelength. With a light microscope, the smallest objects you can make out are about 1/4 of a micron wide. To see still smaller objects, you must use something with a shorter wavelength than light. Because of quantum physics, even seemingly particulate objects such as electrons have a wave character and a wavelength, and fast moving electrons have much shorter wavelengths than light. Electron microscopes can resolve details down to about 1/2 the electron wavelength (in principle) and that brings their resolution down toward the level of individual atoms.

But to see a nucleus, which is much smaller than an atom, you need particles with even smaller wavelengths than are available in electron microscopes. The electrons in particle accelerators have such small wavelengths that they can resolve features as tiny as nuclei. However, the particles making up nuclei are always moving so that the "images" formed by accelerators are blurry. Nonetheless, it's possible to learn much about the structure of nuclei from these accelerator experiments. In fact, people now look at features even smaller than nuclei. They are presently looking at the individual nucleons (protons and neutrons) that make up nuclei and even at the quarks that make up those nucleons.


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