Why do electron microscopes have higher resolution than optical microscopes?
The magnification of an optical microscope is smaller than that of an electron microscope. An optical microscope can only observe microstructures, such as cells, chloroplasts, etc., while an electron microscope can observe submicroscopic structures, that is, it can see the structure of organelles, viruses, bacteria, etc.
An electron microscope projects an accelerated and concentrated electron beam onto a very thin sample. The electrons collide with atoms in the sample and change direction, thereby producing solid angle scattering. The size of the scattering angle is related to the density and thickness of the sample, so images with different light and dark colors can be formed. The image will be displayed on imaging devices (such as fluorescent screens, films, and photosensitive coupling components) after magnification and focusing.
Since the de Broglie wavelength of electrons is very short, the resolution of transmission electron microscopes is much higher than that of optical microscopes, which can reach 0.1~0.2nm, and the magnification is tens of thousands to millions times. Therefore, transmission electron microscopy can be used to observe the fine structure of a sample, and can even be used to observe the structure of just a row of atoms, which is tens of thousands of times smaller than the smallest structure that can be observed with an optical microscope. TEM is an important analytical method in many scientific fields related to physics and biology, such as cancer research, virology, materials science, nanotechnology, semiconductor research, etc.
Why does an optical microscope have the highest resolution when using an oil lens?
Oil lens is one of the optical microscopes. When used, the lens is immersed in oil (usually cedar oil) to observe finer structures. It is one of the microscopes commonly used in laboratories. The clarity is slightly higher than that of ordinary optical microscopes. It is used for Observe chlamydia, bacteria, cell organelles, etc.
The lens of the oil lens is very small. When the light passes through the air between the glass slide and the oil lens, refraction or total reflection occurs due to the different density of the medium, which reduces the light entering the lens and makes the object image unclear. If the oil lens and the carrier are Adding cedar oil (n=1.515), which is similar to the refractive index of glass (n=1.52), between the glass slides will increase the light entering the lens, enhance the brightness of the field of view, and make the object image bright and clear.
Due to the small size of bacteria, in morphological studies of bacteria, it is often necessary to use a microscope oil lens to observe more clearly. Therefore, one must be proficient in the use and protection of oil lenses.
