Why electron microscopes offer higher resolution
As the name suggests, an electron microscope is a microscope that uses an electron beam as an illumination source. Since an electron beam can be bent under the action of an external magnetic or electric field, forming a phenomenon similar to the refraction of visible light through glass, we can make use of this physical effect to create a "lens" for the electron beam, and thus develop an electron microscope. As a transmission electron microscope (TEM) is characterised by the fact that we use the electron beam that passes through the sample to image it, which is different from a scanning electron microscope (Scanning Electron Microscope, SEM). As the wavelength of the electron wave is much smaller than the wavelength of visible light (100kV of the wavelength of the electron wave is 0.0037nm, while the wavelength of violet light is 400nm), according to optical theory, we can expect the resolution of the electron microscope should be much better than the optical microscope. In fact, the resolving power of modern electron microscopes has been up to 0.1 nm. senior physics elective book on the more detailed (photoelectric effect behind the small information)
Why optical microscopes have the highest resolution when using oil mirrors
Oil microscope, one of the optical microscope, when used, the lens immersed in oil (usually cedar oil), used to observe the finer structures, is one of the common laboratory microscope, the clarity is slightly higher than the ordinary optical microscope, used to observe the chlamydia, bacteria, organelles and so on.
The lens of the oil mirror is very small, the light through the air between the slide and the oil lens, due to the density of the medium is different, refraction or total reflection occurs, so that the light emitted into the lens is reduced, the object image is not clear. If you add cedar oil (n=1.515), which has a refractive index similar to that of glass (n=1.52), between the oil mirror and the slide, more light enters the lens and the field of view is brightened, making the object bright and clear.
Because of the small size of bacteria, so in the morphological study of bacteria, often need to use the microscope oil lens, in order to observe more clearly. Therefore, it is necessary to master the use of oil mirror and protection method.
