when do you use the fine adjustment knob

The fine adjustment knob is used after the initial focusing with the coarse adjustment knob to make precise, minute adjustments to the focus for optimal clarity and detail. It is especially used when viewing small or intricate structures under a microscope to sharpen the image and reveal finer details. The fine adjustment knob moves the objective lens very slightly, allowing delicate tuning without introducing vibrations or risking damage to the specimen, which is crucial for high magnification observations. In short, the fine adjustment knob is used for precise focusing once the rough focus is achieved with the coarse adjustment knob, to bring the specimen into clear, sharp focus.