USING A COMPOUND MICROSCOPE
How to Use a Compound Microscope
Familiarization: First, familiarize yourself with all the parts of a microscope so that you can easily
move from one part to another during operation.
Moving and Placement: Always, carry your microscope in both hands. Grasp the arm with one hand
and place the other hand under the base for support. Always place the microscope on a level and
stable surface. Be careful after the scope has been on, the light bulb will be hot.
Slide Preparation: Microscope slides should always be prepared with a cover slip or cover glass
over the specimen. This will help protect the objective lenses if they touch the slide. To hold the
slide on the stage fasten it with the stage clips. You can push down on the back end of the stage
clip to open it.
Make the table below in you journal and fill it in.
Microscopes
Scanning
(Low)
Power
Eyepiece
Objective Lens
Magnification
10 x
4 x
40 x
ALWAYS start out with this lens, focus and center before moving on!
Medium
Power
10 x
______ x
______ x
Focus (can use course adjustment knob) and center specimen before moving on!
High
Power
10 x
______ x
______ x
Focus (Fine focus knob only!) and center specimen before drawing!
General Advice for Focusing the Microscope: Use a prepared slide to experiment and
figure out what each point listed below means when using a microscope.
1. Be careful not to allow the objective lens to touch the slide as you may break the slide.
2. Finally, remember! When you view a specimen through a microscope, you are viewing an
image through multiple lenses. As a result, the image is upside down and back-to-front so
when you move the slide to the right, the image goes to the left and vice versa!
3. Place the slide on the microscope stage, with the specimen directly over the center of the
glass circle on the stage (directly over the light). Then you have a 9 out of 10 chance of
finding the specimen as soon as you look through the eyepiece!
NOTE: If you wear glasses, take them off; if you see only your eyelashes, move closer.
Be sure to close, or cover your other eye!!
NOTE: If you see a dark line that goes part way across the field of view, try turning the
eyepiece. That dark line is a pointer that will be very valuable when you want to point out
something to your lab partner, or your teacher!
4. If, and ONLY if, you are on LOW POWER, lower the objective lens to the lowest point,
then focus using first the coarse knob, then the fine focus knob. The specimen will be in
focus when the LOW POWER objective is close to the lowest point, so start there and
focus by slowly raising the lens. If you can’t get it at all into focus using the coarse knob,
then switch to the fine focus knob.
5. Adjust the Diaphragm as you look through the Eyepiece, and you will see that more detail is
visible when you allow in LESS light! Too much light will give the specimen a washed-out
appearance. TRY IT OUT!!
6. Once you have found the specimen on Low Power (10x), unless specifically asked to draw it
on low power, center the specimen in your field of view, then, without changing the focus
knobs, switch it to High Power. If you don’t center the specimen you will lose it when
you switch to High Power.
7. Once you have it on High Power remember that you only use the fine focus knob! Do not
remove the slide when it is on High Power.” -- The High Power Objective (40x) is very
close to the slide. Use of the coarse focus knob will scratch the lens, and crack the slide.
You break it, you buy it!
How To Make A Wet Mount: Answer the questions embedded in these instructions in
your journal.
1. Cut a small piece of newspaper that includes a lower case “e”. Place the “e” on a slide so it is
right side up.
2. Place ONE drop of water directly over the specimen. If you put too much water over the
specimen, then the coverslip will float on top of the water, making it harder to draw the specimens
as they float past the field of view!
3. Place the coverslip at a 45 degree angle (approximately), with one edge touching the water drop,
and let go.
4. Focus on scanning power, center and focus on medium power. Draw the “e” as it appears when
viewed through the eyepiece.
5. Have your lab partner move the slide away from your body while you are looking through the
lens. Which direction does the slide appear to move when viewed through the eyepiece?
6. Have your lab partner move the slide toward the right while you are looking through the
lens. Which direction does the slide appear to move when viewed through the eyepiece?
Care & Maintenance of Your Microscope
To correctly put the microscope away, you must complete the following basic steps:
1.
When finished viewing, lower the stage, click the low power lens into position and remove
the slide.
2. Switch off the microscope when not using.
3. Avoid touching the glass part of the lenses with your fingers. Use only special lens paper to
clean the lenses.
4. Dust is the number one enemy of a microscope, so always keep your microscope covered
when not in use. When not in use for extended periods, replace the microscope in its
cupboard.