Final answer:
When using a light microscope, it is recommended to use the coarse focusing knob before the fine focusing knob. This allows for quick and approximate focusing of the specimen before fine-tuning it with the fine focus knob.
Step-by-step explanation:
When using 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 is used for large-scale movements with lower magnification objective lenses (such as 4x and 10x), while the fine focusing knob is used for small-scale movements with higher magnification objective lenses (such as 40x and 100x). Adjusting the focus with the coarse focusing knob first allows you to quickly bring the specimen into view and approximately focus it, making it easier to fine-tune the focus using the fine focusing knob.