What is the difference between electron microscope and light microscope
At present, there are not only optical microscopes that can magnify more than a thousand times, but also electron microscopes that can magnify hundreds of thousands of times, allowing us to have a deeper understanding of the laws of biological life activities. Most of the experiments stipulated in the general middle school biology syllabus must be completed through a microscope. Therefore, the performance of the microscope is the key to good observation experiments.
A microscope is a sophisticated optical instrument with a history of more than 300 years. Since the advent of the microscope, people have seen many tiny organisms and the basic units that make up living organisms - cells that were previously invisible.
In summary, the main differences between electron microscopes and optical microscopes are as follows:
1. The imaging principle is different. In an electron microscope, the electron beam acting on the sample to be inspected is enlarged by an electromagnetic lens, and then strikes the fluorescent screen to form an image or acts on the photosensitive film to form an image. The difference in electron density is due to scattering caused by the collision of incident electrons with atoms of matter when the electron beam acts on the sample under test. Since different parts of the sample scatter electrons differently, the electron image of the sample is presented in different shades; the object image of the sample under an optical microscope shows a difference in brightness, which is caused by the difference in the amount of light absorbed by different structures of the sample .
2. The preparation methods of the samples are different. The preparation procedure of tissue and cell specimens for electron microscope observation is complex, technically difficult, and expensive. Special reagents and operations are required in material extraction, fixation, dehydration, and embedding. Finally, the embedded tissue blocks need to be placed in an ultra-thin microtome to cut into ultra-thin specimens with a thickness of 50-100 nm; while the specimens observed by an optical microscope are generally placed on glass slides, such as ordinary tissue section specimens, cells Capsule specimens, tissue pressing specimens and cell drop specimens, etc.
three. The light source is different. The illumination source used in electron microscopes is the flow of electrons emitted by an electron gun; while the illumination source of optical microscopes is visible light (daylight or lamps), because the wavelength of the electron flow is much shorter than the wavelength of light waves, the magnification and resolution of electron microscopes are significantly higher. at the wavelength of light. Light microscopy.
Four. The lens is different. The objective lens used for magnification in electron microscopes is an electromagnetic lens (a ring-shaped electromagnetic coil that can generate a magnetic field in the central part); while the objective lens of an optical microscope is an optical lens made of glass. The electromagnetic lens in the electron microscope has three groups, which are equivalent to the functions of the condenser, objective and eyepiece in the light mirror.
What is an optical microscope:
Optical microscopes use optical principles to magnify and image tiny objects that cannot be resolved by the human eye, thereby extracting microscopic structural information.
What is an electron microscope:
Electron microscope is a large-scale instrument that uses electron beam as illumination source, through multi-stage magnification of electron flow and electromagnetic lens, the sample is transmitted or reflected and imaged on a fluorescent screen, while optical microscope uses visible light. Light illumination is an optical instrument that creates magnified images of tiny objects.
