Correct use and maintenance of the hottest optical

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The correct use and maintenance of optical microscope as the most commonly used instrument in biological experiments, whether the microscope can be used correctly is directly related to the success or failure of many biological experiments. It should be an extremely important content of biology experiment teaching in middle school to point out some mistakes in students' use of microscope and guide students to use microscope correctly. In the practice of biology teaching, through the observation of students' operation process using microscope and some problems reflected in students' experimental examination, the author believes that the following points need to be emphasized by teachers in lectures

I. Problems of correct installation

before using the microscope, first install the eyepiece and objective lens of the microscope. The installation of the eyepiece is relatively simple. The main problem lies in the installation of the objective lens. Because the objective lens is expensive, it is easy for students to fall to the ground and cause lens damage if the thread is not closed well during installation. Therefore, for the sake of safety, it is emphasized that students should hold the objective lens with the index finger and middle finger of their left hand when installing the objective lens, and then install the objective lens with their right hand, so that even if it is not installed, it will not fall to the ground

second, the problem of correct light alignment

light alignment is a very important step when using a microscope. Some students turn an objective lens at random to face the light hole, rather than adopting the "particle fire separation film" technology to align the light with a low power lens as required. I like to use one hand when turning the reflector, and often pull it down. Therefore, when guiding students, teachers must emphasize the use of low-power mirrors for light. When the light is strong, use small apertures and flat mirrors, and when the light is weak, use large apertures and concave mirrors. The reflectors should be rotated with both hands until you see a uniform and bright circular field of vision. After the light is aligned, do not move the microscope casually, so as to prevent the light from entering the light hole through the reflector accurately

third, the problem of using the quasi focal screw correctly

using the quasi focal screw to adjust the focal length and find the object image can be said to be the most important step in the use of the microscope, and it is also the most difficult step for students. Students are prone to the following errors in the operation process: first, focus directly under the high-power mirror; Second, no matter whether the tube rises or falls, the eyes are always looking at the field of vision in the eyeglass; Third, we don't know the critical value of the object distance. When the object distance is adjusted to 2 ~ 3 cm, it is still rising, and the speed of rotating the quasi focal screw is very fast. The first two errors often cause the objective lens to collide with the loading and damage the loading or lens, while the third error is the most common phenomenon when students use the microscope. In view of the above errors, the teacher must emphasize to the students that adjusting the focal length can be used safely. It must be adjusted in the low power lens. First, turn the coarse focus screw to make the lens barrel slowly drop, and the objective lens is close to the slide, but be careful not to let the objective lens touch the slide. In this process, the eye should look at the objective lens from the side, then look into the eyepiece with the left eye, and slowly adjust the coarse focus screw in reverse, so that the lens barrel slowly rises, Until you see the object image, at the same time, explain to the students that the object distance of the general microscope is about 1 cm, so if the object distance has been far more than 1 cm, but you still don't see the object image, it may be that the specimen is not in the field of vision or rotating the coarse focus has a high safety factor, and the spiral speed is too fast. At this time, you should adjust the loading position, and then repeat the above steps. When there is a fuzzy object image in the field of vision, you should change to the fine focus spiral adjustment, Only in this way can we narrow the search scope and improve the speed of finding objects and images

IV. the problem of objective lens conversion

after using a low power lens, students often like to use their fingers to directly push and rotate the objective lens, which is considered to be labor-saving, but it is easy to deflect the optical axis of the objective lens, because the material of the converter is soft, the accuracy is high, and the force on the thread is uneven, which is easy to loosen. Once the thread is damaged, the whole converter will be scrapped. Teachers should guide students to hold the lower rotating plate of the converter to convert the objective lens

v. correct use of eyes

when observing objects with a microscope, both eyes should be opened at the same time, and the left eye should look into the eyepiece. However, many students often fail to do this. They like to cover their right eyes with their hands or simply close their right eyes, which is not in line with the observation requirements of the experiment. This bad habit will cause fatigue in their left eyes, and they can't draw while observing. While pointing out this problem of students, teachers should demonstrate concretely, telling students to keep their left eye as close as possible to the eyepiece, and their right eye try to look into the field of vision. Such repeated training will meet the requirements of opening both eyes at the same time. Or you can also do the following exercise: open your eyes, stand between your eyes with a piece of paper or palm, in front of your nose, so that your left and right eyes can't look at the opposite side of each other, and then consciously look at the left side first, and then the right side. Do this 3 to 5 times every day, morning and evening, and you can learn it in less than a week

maintenance points of optical microscope

(I) it is necessary to master and strictly implement the use procedures

(II) when taking out and delivering the microscope, be sure to hold the curved arm with one hand and hold the base with the other hand. The microscope cannot be tilted to prevent the eyepiece from sliding out of the upper end of the tube. Handle the microscope with care

(III) when observing, do not move the position of the microscope casually

(IV) all optical parts of the microscope can only be wiped with special lens wiping paper and solution. It is not allowed to wipe with other objects indiscriminately, and it is not allowed to touch the lens with your fingers, so as to prevent sweat from polluting the lens

(V) keep the microscope dry and clean to avoid dirt, water and chemical reagents

(VI) when converting the objective lens, do not move the animal lens lens, but only turn the converter. Now the microscope has electric conversion, which is also very convenient to use. It is a development direction

(VII) do not turn the focusing hand wheel at will. When using the micro focusing - Wang Shugu (Technical Consultant) knob, use light force, rotate slowly, and don't turn hard when it doesn't move

(VIII) it is not allowed to disassemble the parts on the microscope at will, and it is strictly forbidden to disassemble the objective lens at will, so as not to damage the screw port of the converter, or after the screw port is loose, the low-power and high-power objective lens will be out of focus during conversion

(IX) when using a high-power objective lens, do not use the coarse focusing hand wheel to adjust the focal length, so as to avoid moving too far and damaging the objective lens and glass slide

(x) adjust the light source to the minimum after use to prolong the service life of the bulb

the wrong use or operation of the microscope is a common phenomenon in biological experiments. As long as we take it seriously, consciously correct it, overcome it, and skillfully and correctly use the microscope, we can do it

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