explain why only the fine adjustment knob should be used when focusing a specimen using the high power objective lens of the light microscope

When using the high power objective lens of a light microscope, only the fine adjustment knob should be used for focusing on a specimen for several reasons:

1. Protection of the Lens and Slide: The high power objective lens is very close to the slide. Using the coarse adjustment knob, which moves the stage a significant amount, could potentially crash the lens into the slide, damaging both the lens and the slide.

2. Precision: The fine adjustment knob allows for small, precise movements. This is necessary when using the high power objective lens because the depth of field (the thickness of the specimen that is in focus) is very small. Small adjustments are needed to bring different parts of the specimen into focus.

3. Image Quality: Using the fine adjustment knob helps to achieve a clearer image. When viewing a specimen under high power, the image can easily become blurry if the coarse adjustment knob is used. The fine adjustment knob allows for slight changes, which can improve the quality of the image.

In conclusion, when using the high power objective lens of a light microscope, it's crucial to use the fine adjustment knob to protect the equipment, achieve precise focusing, and ensure the best possible image quality.