Final answer:
It's best to start with the low power objective lens when focusing a light microscope because it has a larger field of view and greater depth of field, making it easier to locate and center the specimen while minimizing the risk of lens damage.
Step-by-step explanation:
When focusing a light microscope, it is best to use the low power objective lens first for several reasons. One reason is that the low power objective lens has a larger field of view and greater depth of field. This makes it easier to locate the specimen on the slide. After finding and centering the specimen under the low power objective, one can then switch to higher magnification objectives with a finer focus.
Also, the risk of the lens hitting the slide is minimized when starting with a low power lens due to the greater working distance. Therefore, beginning with the low power objective is an important step to effectively and safely view the cells under a microscope.