Why can't smaller things be seen with a light microscope?
A microscope is an optical instrument composed of a lens or a combination of several lenses, which can magnify tiny objects into images that people can see with the naked eye. Since the invention of the microscope in the 17th century, it has provided powerful assistance to biologists and medical scientists in the discovery of bacteria and microorganisms. The current optical microscope can magnify objects up to 1500 times, and even very tiny cells, bacteria, viruses and other objects can be seen clearly under the microscope.
But even the seemingly powerful light microscope has its limits. Because the microscopic world is infinite, very small substances also have smaller components, and optical microscopes can only see things larger than 0.2 microns. If you want to observe smaller things, it can't do anything. Why is this?
It turns out that light is also a kind of wave, and its wavelength is 0.4 microns. If it encounters something smaller than half its wavelength during propagation, it will go around directly. This situation is called diffraction of light. Under an optical microscope, once the light is diffracted, the light will become some extremely small circles or arcs, and we can only see a few fuzzy spots, but not the specific outline of the object. Because of this, optical microscopy has remained largely unchanged since the 19th century.
So if you want to see even smaller things, you have to turn to the electron microscope.
