Several points on the correct use of optical microscopes
1. Correct installation issues
Before using a microscope, you must first install the eyepieces and objective lenses of the microscope. The installation of the eyepiece is relatively simple. The main problem lies in the installation of the objective lens. Since the objective lens is relatively expensive, if the threads are not closed properly during installation, it will easily fall to the ground and cause damage to the lens. Therefore, for the sake of safety, it is emphasized that the user should not install the objective lens when installing the objective lens. Hold the objective lens with the index and middle fingers of your left hand, and then install the objective lens with your right hand so that it will not fall to the ground even if it is not installed properly.
2. The problem of correct light alignment
Aligning the light is a very important step when using a microscope. When aligning the light, some students just turn an objective lens to face the light aperture instead of using a low-power lens to align the light as required. I like to use one hand when turning the reflector, and often pull the reflector down. Therefore, when instructing students, teachers must emphasize the use of low-power mirrors to focus the 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 turned with both hands. When looking at to a uniformly bright circular field of vision. After the light is aligned, do not move the microscope casually to prevent the light from entering the light aperture accurately through the reflector.
3. Problems with correct use of quasi-focus spiral
Using the focus screw to adjust the focus and find the object image can be said to be the most important step in using a microscope, and it is also the step that students find most difficult. Students are prone to make the following mistakes during operation: First, they adjust the focus directly under a high-power lens; Second, their eyes always look into the eyepiece to see the field of view regardless of whether the lens barrel rises or falls; Third, they do not understand the critical value of the object distance. When the distance is adjusted to 2 to 3 cm, it is still being adjusted upward, and the focus screw is turned very quickly. The first two errors often cause the objective lens to interfere with the mounting film and damage the mounting film or lens, while the third error is the most common phenomenon when students use microscopes. In response to the above errors, teachers must emphasize to students that when adjusting the focal length, the focus must be adjusted at low magnification. First, turn the coarse focus screw to slowly lower the lens barrel. The objective lens is close to the glass slide, but be careful not to let the objective lens touch the glass slide. During this process, the eyes 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 the reverse direction, so that the lens barrel slowly rises until the object image is seen, and explain to the students at the same time Generally, the object distance of a microscope is about 1 cm, so if the object distance is far more than 1 cm but you still cannot see the object image, it may be that the specimen is not in the field of view or the coarse focus screw is turned too fast. At this time, you should adjust Set the film loading position, and then repeat the above steps. When a blurry object image appears in the field of view, you must switch to the fine focus screw adjustment. Only in this way can you narrow the search range and increase the speed of finding the object image.
