Which lens should you start with when using a microscope?

• A. x4
• B. x10
• C. x40
• D. x100

Answer: (A)

Starting with the lowest power objective is best because it gives the widest field of view and the most forgiving focus. This makes it easy to locate the specimen on the slide and center it in the viewing area. At this level you can use the coarse adjustment to bring the image into rough focus without losing the specimen, and you avoid the risk of crashing a higher-power lens into the slide. Once the specimen is centered and roughly sharp, you switch to higher magnifications to examine finer details, using the fine adjustment to sharpen the image and adjust lighting as needed. Jumping straight to a high-power objective makes it harder to find the sample and can make focusing more difficult or risky.