Final answer:
When focusing a light microscope, it is best to adjust the focus using the coarse focusing knob before using the fine focusing knob.
Step-by-step explanation:
When focusing a light microscope, it is best to adjust the focus using the coarse focusing knob before using the fine focusing knob. The coarse focusing knob moves the stage forward and back, while the fine focusing knob is used for small-scale movements. This is because the coarse focusing knob is designed for large-scale movements, which helps to quickly bring the specimen into focus, while the fine focusing knob allows for more precise adjustments to achieve optimal clarity.