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Teacher's Guide to Microscopes

Are you planning to purchase some new microscopes to replace old ones or to meet the needs of increased enrollment? If you’re a first-time buyer, the task can seem daunting. This brief guide explains the basics of microscopes and their applications, helping you choose the right models for your classroom or laboratory.

The 2 basic types of microscopes: Compound microscopes and Stereomicroscopes

Compound 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 microsized 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.

Stereomicroscopes

Stereomicroscopes, sometimes referred to as dissecting microscopes, provide low-power magnification with a wide field of view. They are used to observe macrosized specimens such as rocks, fossils, macroorganisms, circuit boards, and the like. Stereomicroscopes usually have a binocular head.

Specimens viewed with a stereomicroscope can be illuminated by light below the stage, above the stage, or both. The specimen need not be thin enough for light to pass through it from below. Specimens viewed through stereomicroscopes usually are not mounted on slides.

Specimens viewed through a stereomicroscope have a 3-D appearance. Total magnification usually ranges from 10× to 40×. As in the compound microscope, magnification is accomplished by the combination of the eyepiece lens and the objective lens in the nosepiece.

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