Using A Compound Light Microscope

Proper Handling and Use of the Compound Light Microscope

1. Carry the microscope to your lab table by using both hands, one supporting the base and the other holding the arm of the microscope. Hold the microscope close to your body

2. Place the microscope on the lab table at least 5 cm (2 in.) from the edge of the table.

3. Check to see what type of light source the microscope has. If the microscope has a lamp, plug it in and make sure that the cord is out of the way If the microscope has a mirror, adjust it to reflect light through the hole in the stage.

CAUTION If your microscope has a mirror, do not use direct sunlight as a light source. Using direct sunlight can damage your eyes.

CAUTION If your microscope has a lamp, be careful not to touch the bulb of the lamp. The bulb can get very hot.

4. Adjust the revolving nosepiece so that the low-power objective is in line with the body tube.

5. Place a prepared slide over the hole in the stage, and secure the slide with the stage clips.

6. Look through the eyepiece, and move the diaphragm to adjust the amount of light that passes through the specimen.

7. Now look at the stage at eye level, and slowly turn the coarse adjustment to raise the stage until the objective almost touches the slide. Do not allow the objective to touch the slide.

8. While looking through the eyepiece, turn the coarse adjustment to lower the stage until the image is in focus. Never focus objectives downward. Use the fine adjustment to attain a sharply focused image. Keep both eyes open while viewing a slide.

9. Make sure that the image is exactly in the center of your field of vision. Then, switch to the high-power objective. Focus the image with the fine adjustment. Never use the coarse adjustment at high power.

10. When you are finished using the microscope, remove the slide. Clean the eyepiece and objectives with lens paper, and return the microscope to its storage area.

Procedure for Making a Wet Mount

1. Use lens paper to clean a glass slide and coverslip.

2. Place the specimen that you wish to observe in the center of the slide.

3. Using a medicine dropper, place one drop of water on the specimen.

4. Position the coverslip so that it is at the edge of the drop of water and at a 45° angle to the slide. Make sure that the water runs along the edge of the coverslip.

5. Lower the coverslip slowly to avoid trapping air bubbles.

6. If a stain or solution will be added to a wet mount, place a drop of the staining solution on the microscope slide along one side of the coverslip. Place a small piece of paper towel on the opposite side of the coverslip.

7. As the water evaporates from the slide, add another drop of water by placing the tip of the medicine dropper next to the edge of the coverslip, just as you would if you were adding stains or solutions to a wet mount. If you have added too much water, remove the excess by using the corner of a paper towel as a blotter. Do not lift the coverslip to add or remove water.




Scientists throughout the world use the Système International d'Unités, or International System of Units. It is usually referred to simply as SI. You will often use SI units to express the measurements that you will make in the laboratory. Most measurements in this book are expressed in SI units.

SI is a decimal system; that is, all relationships between SI units are based on powers of 10. Most units have a prefix that indicates the relationship of that unit to a base unit. For example, the SI base unit for length is the meter. A meter equals 100 centimeters (cm), or 1,000 millimeters (mm). A meter also equals 0.001 kilometers (km). Table 1 summarizes the prefixes and abbreviations that are commonly used to represent SI units.

SI Units

TABLE 1 Some SI Prefixes



Factor of base unit


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