The Compound Microscope

There are a number of different kinds of microscopes available today, but the basic compound microscope is still widely used in middle school and high school labs. The teach often tells students to carry the microscope by placing one hand holding the arm while the other hand is under the base. Because the microscope is expensive to purchase or repair is is reasonable to expect students and others to properly carry one when necessary.

In general when a slide is place under the clips on the microscope stage the student is told to turn the course adjustment to a position that is very close to the top of the slide, but not touching it. They are told to look from the side to make this initial adjustment. They are told that from this point they should only adjust upward from the slide until the view through the eyepiece is generally in focus. The reason for adjustment of the course adjustment only in an upward direction is to prevent the magnification lens from touching and perhaps placing enough pressure on the slide breaking the slide or damaging the magnification lens. Usually the student is instructed to start with the lower amount of magnification at first. When the slide is in as much focus as possible with the course adjustment it can then be focused a it more with the fine adjustment.

In some cases the fine adjustment will focus only portions of what is eing viewed at one time ecause the specimen may have enough thickness to cause the focus to change as different layers or parts are brought into and out of focus. Stains used in the preparation of the slide may also cause some differences in the focus needed. In most cases the use of a cover slip is advised to keep the magnification lens from actual contact with the specimen.

The light source may be a mirror but in many labs the use of a powered light source is often used since relying on sunlight can not be expected with the design of many uildings today. Some of the new microscopes have the ability to project the image or to send the image to a monitor which makes viewing much easier today.

The nosepiece can revolve to place a different magnification in position, but students should take care when they use this process because there is the possibility that the different magnification lens will hit the slide. Although microscopes are typically designed so changing the magnification will not cause the new lens to hit the slide, it can still happen. As a student turns the nosepiece they shoudd observe from the side to be certain the new lens does not hit the slide.

The diaphragm is used to make adjustments to the amount of light getting to the slide and this adjustment can improve the visibility of some specimens. In some cases "top" lighting can be used to get better views. Students are often asked to draw what they see through the microscope and this helps the instructor evaluate if they are actually seeing what they are supposed to be seeing.

It is very exciting when students view actual living organisms that may be living in a single drop of pond water.There are a number of biological supply companies that can quickly ship live biological specimens that can be viewed under a microscope or ones that are already prepared on slides.