The benefit of a high-power objective lens is that it provides the most magnification possible with most standard, monocular (single) eyepiece microscopes. It is what's required to provide the most magnification -- that is, to get as close as possible to the specimen being examined.
How a High-Power Objective Lens Works
The magnification provided by a compound optical microscope is a product of the power of the eyepiece (ocular lens) and the objective lens. A final magnification of 1000x is possible with most standard optical microscopes as the normal magnifications of the objective and ocular are 10x and 100x or 10x 100 = 1000x. A magnification of 1000x means the specimen can be seen at 1,000 times its actual size.
The Advantage Provided by a High-power Objective Lens
The advantage of a high power objective lens is that it provides a higher degree of magnification, which allows you to “zoom” in closer to the object being studied and see more detail. However, a lower power lens will provide a wider field of vision. This is analogous to using a magnifying glass to examine an insect. As you move the magnifying glass closer and closer to the insect, you will see more of it but less of the ground around it.
Choosing a Microscope
If you are a teacher charged with the responsibility of buying microscopes for classes such as biology, genoscience, materials science or microbiology, it's important to choose a microscope with a high-power objective lens to give your students the most magnified view possible of the specimens they will be examining. Be sure that the microscopes you select are compound microscopes with nose pieces that have at least three or, if possible, four objective lenses. If you select microscopes with three objective lenses, they should be 4x (4 times actual size), 10x (10 times actual size) and 100x (100 times actual size).
Other Considerations in Choosing a Microscope
When choosing microscopes that will be used by students, it is important to select ones that are sturdy and "student proof." If you need to use a microscope in conjunction with a monitor -- to display a picture all your students can see simultaneously -- be sure to choose a digital microscope. These microscopes use a CCD camera to examine samples (instead of an eyepiece) so the images can be shown directly on a computer monitor.