Why does an electron microscope have a higher resolution than an optical microscope?
The magnification of an optical microscope is smaller than that of an electron microscope. An optical microscope can only observe microscopic structures such as cells and chloroplasts, while an electron microscope can observe submicroscopic structures, that is, the structure of organelles as well as viruses, bacteria, etc
An electron microscope projects an accelerated and focused electron beam onto a very thin sample, where the electrons collide with atoms in the sample and change direction, resulting in solid angle scattering. The size of the scattering angle is related to the density and thickness of the sample, so it can form images with different brightness and darkness. The images will be displayed on imaging devices (such as fluorescent screens, films, and photosensitive coupling components) after magnification and focusing.
Due to the very short de Broglie wavelength of electrons, the resolution of transmission electron microscopy is much higher than that of optical microscopy, reaching 0.1-0.2nm and magnification of tens of thousands to millions of times. Therefore, the use of transmission electron microscopy can be used to observe the fine structure of samples, and even to observe the structure of only one column of atoms, which is tens of thousands of times smaller than the smallest structure that can be observed by optical microscopy. TEM is an important analytical method in many scientific fields related to physics and biology, such as cancer research, virology, materials science, as well as nanotechnology, semiconductor research, and so on.
