Teacher’s Guide to Microscopes

Compound microscopes are the type that most people think of when they hear the word “microscope.” Compound microscopes typically provide high-power magnification with a narrow field of view. They are used to view micro-sized specimens that are thin enough to allow light to pass through them. These include microorganisms, tissue samples, cells, and the like. Specimens must be mounted on a glass or plastic slide prior to viewing.

Slides to be viewed are placed on the microscope’s stage and illuminated by light from below the stage. Magnification usually ranges from 40× to 1,000×, and is accomplished by the combination of the microscope’s eyepiece lens and one of its objective lenses located in the rotating nosepiece. The magnification powers of both lenses are multiplied together to determine the total magnification. For example, a 10× eyepiece and a 40× objective yield a total magnification of 400×.

Compound microscopes are available with monocular (one eyepiece), binocular (2 eyepiece), and trinocular (3 eyepiece) heads. Monocular compound microscopes are sufficient for most beginning student (upper elementary through high school) work. Binocular compound microscopes should be used for more advanced work, i.e., advanced high school and up, because they reduce eyestrain during long viewing sessions. Compound microscopes are also available with trinocular heads, which enable binocular viewing with a separate eyepiece for cameras or other media devices.

A graduated mechanical stage is an essential accessory for compound microscopes used in high school and college classes. It allows the student to position the slide precisely in the field of view. This makes it possible to perform measurements and to examine the entire specimen in detail.