Which adjustment should be used first when focusing a specimen under a compound microscope?

Which adjustment should be used first when focusing a specimen under a compound microscope?

• A. Fine adjustment knob
• B. Eyepiece
• C. Coarse adjustment knob
• D. Diaphragm

Answer: (C)

Focusing a specimen under a compound microscope is done in stages: start with the coarse adjustment knob because it makes larger, quicker movements that bring the image into view. Begin with the lowest magnification objective so you can locate the specimen easily, then use the coarse knob to raise or lower the stage until you see the image roughly in focus. After that, switch to the fine adjustment knob to sharpen the details precisely. The eyepiece simply provides the view, and the diaphragm adjusts light, which helps with contrast but doesn’t establish focus. Once you have a sharp image at the low power, you can switch to higher magnifications and use the fine adjustment again to maintain a crisp view.

Focusing a specimen under a compound microscope is done in stages: start with the coarse adjustment knob because it makes larger, quicker movements that bring the image into view. Begin with the lowest magnification objective so you can locate the specimen easily, then use the coarse knob to raise or lower the stage until you see the image roughly in focus. After that, switch to the fine adjustment knob to sharpen the details precisely. The eyepiece simply provides the view, and the diaphragm adjusts light, which helps with contrast but doesn’t establish focus. Once you have a sharp image at the low power, you can switch to higher magnifications and use the fine adjustment again to maintain a crisp view.