Types of microscopes and their uses
* Microscope *: It is a device that specializes in magnification of small objects and objects, which facilitates their study. It is especially useful for biologists who study living organisms, and cells that require advanced methods and techniques to facilitate their study. The function of the microscope is not limited to magnification, that is, to show the material being studied in a larger size, but rather to show details, which is known as resolution.
Types and uses of microscopes Optical microscopes Optical microscopes use light and a range of lenses to enlarge the sample; As it is one of the most common and simpler types of microscopes, it is also low cost, which makes it ideal for use in education, the medical field, and for amateurs as well, and it has the advantages of providing the ability to monitor the activities of living cells, such as movement, division, and food absorption. [2] Simple microscope is one type of optical microscope, which is a microscope consisting of only one lens, [3] and optical microscopes are composed of two other types:
1-Compound optical microscope Compound optical microscope: The simplest types of complex optical microscopes consist of an ocular lens through which the sample to be studied can be seen, and an objective lens called this name because it It is close to the object to be enlarged, but the modern complex microscopes are more complicated, and it consists of an eye lens and 2-4 of the objective lenses in addition to a light bulb, or a mirror that directs light towards the transparent glass slide on which the sample is placed. The distance of objective lenses from the sample can be controlled by the large adjuster that is used for close adjustment, and the small adjuster for fine adjustment. The sample - which should be thin - is placed on the glass slide and light is directed to it, so the objective lens magnifies it, then the magnified image passes through the ocular lens that magnifies it 10 times; That is 10 x. The ability to magnify the microscope for the sample can be calculated by multiplying the magnification of the objective lens for the sample by the magnification capacity of the ophthalmic lens, so if the objective lens that magnifies the sample is selected 40 times, i.e. 40 x; The sample becomes 40 x 10 magnified 400 times; I.e. 400 x; It means x number of times magnification. Typical magnification of a compound optical microscope is 1500 times, while the discrimination force is 0.2 وميm. [1] [3] (The resolution force or Resolution separation force is defined as the ability to distinguish the shortest distance between two points on
The slice, depending on the wavelength of the light used, increases the microscope's ability to distinguish the small details of the sample the shorter the wavelength of light). [4]
2- Anatomical microscope Anatomical microscope (in English: stereo or dissecting microscope): Anatomical microscope consists of two eye lenses and object lenses, and gives a three-dimensional image of the surface of the sample to be studied and enlarged fifty times or less. Anatomical microscopy is used in anatomy, microscopic surgery, watchmaking, and the study of samples that can be seen with the naked eye such as insects and crystals. [3] [5]
Electron microscope The first electron microscope (in English: Electron Microscope) was built by German engineers Ernst Ruska and Max-Nol in 1931, and we were able to enlarge samples only 400 times, and in 1933 Ruska was able to manufacture an electron microscope with a higher accuracy than that That can be obtained using optical microscopes; As this model is considered one of the electronic microscopes upon which all modern electronic microscopes are built. An electron microscope is used in many fields. It is used to study microorganisms, cells, biopsy specimens, and the crystal structure of minerals, as well as studies on quality assurance and semiconductor device fabrication. [6] An electron microscope uses a beam of electrons that enlarge bodies instead of Using visible light, and it has a much greater ability to magnify than optical microscopes; The sample can be enlarged two million times, and its ability to show detail is greater; Because the wavelength of electrons is much smaller than the wavelength of light, and its types: [6]
3- Transmission Electron Microscope: This type of microscope is used to study the internal contents of the sample, and its work depends on the release of electrons from a strong electrical source known as Electron gun, and the electrons are focused using electrostatic and electromagnetic lenses. When these electrons collide with the sample, some of them can pass through, while others are dispersed; When the electrons that penetrated the sample exit, they are loaded with information, and when these electrons reach a fluorescent screen covered with phosphorous, the sample image appears to be enlarged. Scanning Electron Microscope: The scanning electron microscope works differently from the transmission electron microscope; This is because the electrons that reach the sample cause the release of secondary low-energy electrons from the sample, then the secondary electrons are then monitored by a screen and a magnified and three-dimensional image of the sample surface is formed. Scanning Transmission Electron Microscope (Reflection Electron Microscope): It is similar to the transmitting electron microscope, except that the image is formed based on monitoring of the rays reflected from the surface of the sample.
And finally-
* The disadvantages of electron microscopes, despite the many benefits offered by electron microscopes; However, it has some drawbacks, including: [2] its high cost, and the maintenance costs are high.
The need for accuracy and expertise when preparing the sample to be studied.
The need to put a thin layer of metal on the sample such as gold; To allow the electrons to be reflected.
It cannot be used to monitor live cells; This is because the sample has to undergo drying and a high dose of radiation which leads to its death.
- It takes up a lot.
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