When using the high power objective on a compound light microscope, only the _____ should be used to focus the image.

• A. stage clip
• B. fine adjustment knob
• C. coarse adjustment knob
• D. diaphragm lever

Answer: (B)

Verified step by step guidance

1. Understand the function of the different focusing knobs on a compound light microscope: the coarse adjustment knob and the fine adjustment knob.
2. Recall that the coarse adjustment knob is used for large, initial focusing movements, typically with low power objectives to bring the specimen roughly into focus.
3. Recognize that the high power objective lens requires very precise focusing because it magnifies the image more, making the depth of field shallower.
4. Therefore, when using the high power objective, only the fine adjustment knob should be used to make small, precise adjustments to the focus without damaging the slide or lens.
5. Confirm that other options like the stage clip and diaphragm lever are not related to focusing but rather to holding the slide in place and controlling light intensity, respectively.