Because the movement is too large and you can break the slide of you turn it the wrong way.
The coarse adjustment knob should never be used when viewing in high power with a compound microscope. When in high power, use the coarse adjustment (the knob smaller than the coarse adj.) to more accurately focus on the subject.
The coarse adjustment knob on a microscope should never be used with the high-power objective lens. This can cause damage to both the lens and the slide being viewed. Instead, it is best used with the low-power or scanning objective lens for initial focusing.
First of all, one should never call it high power, it is morecommonly called the "high objective", yet that is not what this question is asking. To answer the question: You use the fine adjustment knob. This knob should be located near the coarse adjustment knob, on the opposite side of the microscope (at the same height as the coarse adjustment knob), or even as a separate knob protruding from the coarse adjustment knob. The fine adjustment knob is smaller in size. You should never, ever use the coarse adjustment knob under the high objective, you could scratch the microscope slide, cover slip, high objective lens, or in a worst case scenario break the high objective lens.
Using the coarse adjustment knob on high power can potentially damage the microscope or the slide being observed due to the high magnification and close proximity of the objective lens to the slide. It is better to make coarse adjustments on low power to avoid hitting the objective lens against the slide.
Using the coarse adjustment on higher power can risk damaging the lens or the slide because the distance between the lens and the slide is very small. It can also cause the objective lens to hit and break the coverslip or slide. Finer adjustments should be made with the fine adjustment knob when using higher magnifications to prevent this.
For low power you can use the coarse adjustment and fine adjustment for high power you should only use the fine adjustment because on high power, the objective lens is too close to the slide and using the coarse adjustment may scratch the objective lens.
use the fine adjustment knob to get a better view of what you are looking at.For low power you can use the coarse adjustment and fine adjustmentfor high power you should only use the fine adjustment because on high power, the objective lens is too close to the slide and using the coarse adjustment may scratch the objective lens.
use the fine adjustment knob to get a better view of what you are looking at.For low power you can use the coarse adjustment and fine adjustmentfor high power you should only use the fine adjustment because on high power, the objective lens is too close to the slide and using the coarse adjustment may scratch the objective lens.
It is inappropriate to use the coarse adjustment knob when focusing on high-power objectives, typically 40x or higher, as this can lead to damage to the slide or the objective lens by bringing the stage too close to the lens. Instead, fine adjustment should be used for precise focusing at these magnifications. Coarse adjustment is suitable only for low-power objectives, where greater distances between the lens and slide are maintained.
I believe it's the coarse adjustment.
The coarse adjustment knob is typically used with low-power objectives, such as the 4x or 10x magnification lenses, on a microscope. This allows for significant adjustments in focus when initially locating a specimen or bringing it into view. Once the specimen is focused, the fine adjustment knob should be used for precise focusing, especially at higher magnifications. Using the coarse adjustment knob at high power can risk damaging the slide or the objective lens.
The depth of field is so small that a very small vertical travel could shift the focus from the top of the specimen to the bottom. A very fine adjustment must be used, which is why the coarse adjustment screw is implemented.