Issues Concerning the Correct Operation of Microscope Focus Adjustment Screws
Using a quasi focus spiral to adjust the focal length and find the object can be said to be the most important step in microscope use, and it is also a difficult step for students to find. Students are prone to the following errors during the operation process:
One is to focus directly under high magnification;
Secondly, regardless of whether the lens barrel rises or falls, the eyes are always looking into the field of view through the telescope;
Thirdly, there is a lack of understanding of the critical value of object distance. When the object distance is adjusted to 2-3 centimeters, it is still increasing upwards, and the speed of rotating the quasi focus spiral is very fast.
The first two types of errors often cause the objective lens to collide with the mounting, damaging the mounting or lens, while the third type of error is a common phenomenon among students when using microscopes.
In response to the above errors, teachers must emphasize to students that adjusting the focal length must be done by lowering the low-power lens. First, rotate the coarse focus screw to slowly lower the lens barrel and bring the objective lens closer 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 mirror from the side, then use the left eye to gaze into the eyepiece, and slowly adjust the coarse focus screw in reverse to slowly raise the lens barrel until the object image is seen. At the same time, explain to students that the object distance of a microscope is usually around 1 centimeter. Therefore, if the object distance has exceeded 1 centimeter but the object image is still not seen, it may be that the specimen is not in the field of view or the coarse focus screw rotation speed is too fast. At this time, adjust the mounting position and repeat the above steps. When blurry images appear in the field of view, it is necessary to switch to fine focus spiral adjustment. Only in this way can, In order to narrow down the search range and improve the speed of finding objects.
