Question

The fine adjustment knob may be used with all 4 objective lenses

Answer 1

UsinG the standard light microscope, the coarse adjustment knob is routinely used with low-power objective lens because they focus further away from the slide, specimen, and cover-slip. So, you have a range there for making coarse adjustment to the focus. However, when you are using the high-power objective lens, the focus is already very close to the specimen and cover-slip. The coarse adjustment there may accidentally drive these objective lens housing into the cover-slip, specimen and slide, damaging them. Always, when using the high-power objective lens, visually bring the objective lens into "approximate" focus position, then use the "fine" adjustment knob to focus for the best image.....