Name: ________________________________
Per: _____ Date: _____
Introduction to the Compound Light Microscope
Background: "Micro" literally means tiny, "scope" means to view or to look at. Therefore, a microscope
is a tool used to enlarge images of small objects so as they can be studied. The compound light
microscope is a tool containing two lenses, which magnify, and a variety of knobs used to move and
focus the specimen. Since it uses more than one lens, it is sometimes called the compound microscope in
addition to being referred to as being a light microscope.
Please identify the safety symbols for this experiment below.
_________________________
_________________________
Purpose: The purpose of this laboratory experience is:
-to demonstrate the proper procedures used in correctly using the compound light microscope
-to learn how to properly prepare and use a wet mount
-to determine the total magnification of the microscope
-to describe changes in the field of view and light when going from low to high power using the
compound light microscope and how it affects what you actually see as you observe it
-to learn how to properly focus when going from low power to high power
Materials: The following materials are needed to perform this laboratory experience:
-Compound microscope
-Glass slides
-Cover slips
-Eye dropper
-Beaker of water
-letter "e" cut from newsprint
-Scissors
-forceps/tweezers
Procedures:
Obtain a microscope from the cabinet. Record the number of your microscope here: (found on the arm of
the microscope). _____________________________________________
Determining Total Magnification
Locate the numbers on the eyepiece and objective lenses. For each of the situations, record their
magnification in the space provided on the next page:
Eyepiece
Magnification
Objective magnification
Total
magnification
Scanning Lens
X
=
Low Power
X
=
High Power
X
=
1. Write out a formula for determining total magnification of a compound microscope.
___________________________________________________________________________
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Name: ________________________________
Per: _____ Date: _____
Preparing a wet mount of the letter "e”
1. With scissors, cut out the letter "e" from the newspaper.
2. Clean both the slide and the cover slip with a paper towel.
3. Place it on the glass slide so as to look like the figure below:
4. Using your eyedropper, place a drop of water on the letter “e”.
5. Cover it with a clean cover slip by placing the slip at an angle and slowly lowering the slip. See
the figure below.
6. Turn on the microscope and place the slide on the stage making sure the "e" is facing the normal
reading position (see the figure above). Using the course adjustment and scanning lens, move the
stage until the "e" can be seen clearly. Use the fine adjustment knob to sharply focus the image.
Draw exactly what you observe in the space below (Do not draw the arrow!).
Drawing of: ______________________________
Total Magnification: _______________________
Drawn by: _______________________________
Date: ___________________________________
7. How does the orientation of what you see through the eyepiece compare with what you see on the
stage?
____________________________________________________________________________
8. Looking through the eyepiece, move the slide to the upper right area of the stage. What direction
does the image move?
____________________________________________________________________________
9. Now, move it to the lower left side of the stage. What direction does the image move?
____________________________________________________________________________
10. Re-center the slide and change the scope to low power. You will notice the "e" is out of focus.
Do NOT touch the coarse adjustment knob, instead use the fine adjustment to resolve the picture.
Once focused, change to high power. Refocus with the fine adjustment knob ONLY, and draw
the image you see of the letter “e” (or part of it) on high power.
Drawing of: ______________________________
Total Magnification: _______________________
Drawn by: _______________________________
Date: ___________________________________
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Name: ________________________________
Per: _____ Date: _____
11. Locate the diaphragm under the stage. Move it back and forth and explain how light intensity
changes as you do so.
____________________________________________________________________________
12. Remove the slide, wash and dry it, and return it to the proper location.
13. Place the scanning objective in place and lower the stage.
14. Turn off the microscope and wind up the wire around the arm between the light and stage.
15. Cover the scope with the dust cover. Place the scope back in its original space in the cabinet. Pay
attention to the numbered spots.
16. Get a clean up stamp.
1. Images observed under the light microscope are reversed and inverted. Explain what this means.
________________________________________________________________________________
2. Explain why the specimens you observe must be very thin and nearly transparent.
_________________________________________________________________________________
________________________________________________________________________________
3. Explain why the specimen must be centered in the field of view on the scanning lens before going to
higher powers.
_________________________________________________________________________________
_________________________________________________________________________________
4. A microscope has a 20 X ocular (eyepiece) and two objectives of 10 X and 43 X respectively:
a. Calculate the low power magnification of this microscope. Show the formula and all your work.
b. Calculate the high power magnification of this microscope. Show the formula and all your work.
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Name: ________________________________
Per: _____ Date: _____
1. ___________________________
10. __________________________
2. ___________________________
11. __________________________
3. ___________________________
12. __________________________
4. ___________________________
13. __________________________
5. ___________________________
Red lens:
6. ___________________________
Yellow lens:
7. ___________________________
Blue lens:
8. ___________________________
Beige lens:
9. ___________________________
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