Name _________________________
Date _____________
The Compound Microscope
Purpose: To learn the parts of the compound microscope and to learn the basic skills needed to use the
microscope properly.
Materials: Microscope
Microscope slides
Slide of letter "e"
Cover slips
Colored paper
Read the basic rules for using a microscope.
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Always carry the microscope by the arm with the other hand supporting the base.
Keep the microscope pushed back from the edge of your table. Do not leave purses, extra books, etc., on
your lab table.
Periodically clean the lens of your microscope. (CLEAN ONLY WITH LENS PAPER!!!)
Keep the stage dry and always make sure the bottom of your slide is dry before putting it on the
microscope.
5
Never use the coarse adjustment knob while using the high power objectives.
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PLEASE READ AND OBEY THIS VERY CAREFULLY!!!!!!!!!! Always start with the 4x objective;
focus with this objective using the coarse adjustment knob. Once the image is in focus, carefully swing the
high power objectives in place--first the 10x and then the 40x. Focus the high power objectives using
ONLY the fine adjustment knob.
These microscopes are parfocal. This means that the corresponding focal points on all the objectives are in
the same plane. In other words, if the microscope is focused with one lens, it is in focus on the other
lenses.
Return your objective to low power before you put the microscope away.
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PROCEDURE: THE MICROSCOPE and letter "e"
1
Make sure the shortest objective is pointing down. Find each of the parts below on the microscope.
Ocular
Nosepiece
Clips
Body tube
Fine Adjustment Knob
Arm
Diaphragm
Base
Coarse Adjustment Knob
Stage
Mirror
Objectives
2
How many objectives does your microscope have? _____________
3
Look for the whole numbers on the objectives. How many times does each objective magnify?
__________________________________
4
Which objective is closest to the stage when it is pointing straight down? ________________
1 5
Look for the number on the ocular. How many times does the ocular magnify? ___________
6
Put the lowest power (4x) objective in place so it is pointing straight down. Turn the microscope so that
the arm is facing you. Look through the ocular until you see a clear circle of light. This is called your field
of view. How many lenses does the light pass through? ______________
7
To find the total magnification you get with the 4x objective, multiply the magnification of the ocular times
the magnification of the objective. What is your total magnification using the 4x objective? The 10x
objective? The 40x objective?
4x objective: _______________________
10x objective: ______________________
40x objective: ______________________
8
Turn the coarse adjustment knob away from you. Does the stage move up or down? ______________
9
Turn the fine adjustment knob away from you. Does the stage move up or down? ________________
10 Get a clean slide from the supply table. Cut the smallest "e" you can find from the newspaper. The best
size "e" is found in an article in the paper. Do not use an "e" from the title of an article or from the
classified section. Place the "e" on a slide and cover with a cover slip. Place the slide on the stage so that
the "e" is right side up. Observe the "e" with the 4x objective. Compare the position of the "e" through the
microscope with the actual position on the slide.
Is the image in the same position? If not, describe its position under the microscope. _________________
______________________________________________________________________________________
11 While looking in the ocular, slowly move the slide from right to left. Which way does the image move?
____________________________
12 Move the slide away from you. Which way does the image move? _______________________________
13 Making accurate sketches is very important in the study of biology. Try to make a drawing to scale in
relation to the field of view. Label the drawing with three pieces of information: (1) the name of the
specimen, (2) the objective being used as the drawing is made, and (3) the estimated size of the specimen.
Make a sketch of the "e" with the 4x objective.
Sketch of the "e" with the 4x objective.
______________ Name of specimen
______________ Objective used to make drawing
______________ Estimated size of specimen
2 14 Swing the 10x objective into place. Is the field of view larger or smaller with the higher power objective?
___________________________
15 Draw the "e" as seen under the 10x objective. Try to get a good comparison of the difference in size as
seen with the 4x. Be sure to label the drawing with the three things we discussed.
Draw the "e" as seen under the 10x objective.
______________ Name of specimen
______________ Objective used for drawing
______________ Estimated size of specimen
16 Get a clear focus with the 10x objective. Now, VERY CAREFULLY, swing the 40x objective into
position. DO NOT LOWER THE STAGE FIRST!! IT MAY LOOK AS IF IT IS GOING TO HIT THE
STAGE, BUT IT WILL NOT!! It should be just a fraction of an inch above the cover slip. Remember not
to use the coarse adjustment knob with the high power lens. Use the fine adjustment knob to get a clear
image.
What has happened to the size of your field of view? _____________________________________
Draw the "e" as it appears under the 40x objective and label.
____________ Name of specimen
____________ Objective used for drawing
____________ Estimated size of specimen
3 17 As you changed objectives while looking at the "e", did the position of the "e" change? _______________
What happened to the field of view? _______________________________________________________
What happened to the actual size of the specimen? _____________________________________________
18 You must know how to measure the size of the specimen you are looking at under the microscope. What is
the diameter of the 10x field of view in microns? _________________
19 What is the diameter, in microns, of the 40x objective? ____________
PROCEDURE: COLORED PAPER
1
From the magazine or funny paper cut out a small piece of colored paper. Place the colored paper on a
clean dry slide. Place a cover slip on top of the paper. Use the 10x objective.
How does this compare with the picture as seen with the naked eye? ______________________________
______________________________________________________________________________________
Make a sketch of the colored paper as it appears under the microscope.
____________ Name of specimen
____________ Objective used
2
You have just seen an example of the resolving power (resolution) of the microscope. For most people,
two objects that are less than .1 mm apart cannot be seen as separate objects by the naked eye. The
microscope permits us to detect space between objects that are much closer than this. However, it can
spread the objects so far apart that the picture no longer makes sense.
What is resolving power (resolution)? _______________________________________________________
______________________________________________________________________________________
3
How can magnification help us? ___________________________________________________________
4
How can resolution help us? ______________________________________________________________
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How can too much resolving power be a handicap? ____________________________________________
4 Cleaning up the Lab
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Wipe the lenses of your microscope. Dry any water on the stage. Put the low power objective in place,
and rack the objectives as far away from the stage as possible. Return it to the cabinet, placing your
microscope in the proper slot.
Wash and dry your slide and return it to the proper container.
Wash and dry the coverslip if it is glass and return it to the box. Plastic coverslips should be thrown away.
Wipe down your table. You are your partner are completely responsible for keeping your table, and the
area around you. Do not leave anything on the table when you leave the lab.
All other materials should be returned to their proper location.
Please, please, please do not put any solid materials into the sinks!
Final Observations
1
Why do you not use the coarse adjustment knob while using the high power objectives?
2
Why must the bottom of slide and the stage be kept dry? (Hint: It won't hurt the stage!)
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What is a parfocal microscope? What is the advantage of this?
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What is the total magnification using the three objectives of your microscope?
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What is the diameter of the field of view with each objective?
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Was it easier to estimate the diameter of the hair using the 10x or 40x objective? Why? Which estimate do
you think is more accurate?
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What three things should always be given with a drawing?
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When first placing a slide on the microscope, what lens should you begin with? How should you proceed
from there?
5 The Compound Microscope
Student Data Pages - Answers
THE MICROSCOPE and letter "e"
1
Locate and learn each of the following parts of the microscope. Check them off the list below as you find
them.
Ocular
Nosepiece
Clips
Body tube
Fine Adjustment Knob
Arm
Diaphragm
Base
Coarse Adjustment Knob
Stage
Mirror
Objectives
2
How many objectives does your microscope have? 3 or 4 depending on your microscope
3
How many times does each objective magnify? Most student microscopes have three objectives that
magnify 4x, 10x, or 40x.
4
Which objective is closest to the stage when it is pointing straight down? the 40x objective
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Look for the number on the ocular. How many times does the ocular magnify? This can vary depending
on your microscope. Most student microscope will have a 10x ocular.
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How many lenses does the light pass through? 2 - the ocular and the objective
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What is your total magnification using the 4x objective? Total magnification is equal to the ocular times
the objective. The total magnification using the 4x objective would be 40, if the ocular is 10.
The 10x objective? 100
The 40x objective? 400
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Does the stage move up or down? down
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Does the stage move up or down? Down. Students may say that it does not move at all. The fine
adjustment moves the stage such a small amount that students often say the stage is not moving. The
students should be made aware that the fine adjustment moves the stage exactly like the coarse adjustment
only in smaller increments. You may be using microscopes that move the objectives up and down instead
of the stage.
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Is the image in the same position? If not, describe its position under the microscope.
The "e" is in a different position. It has been flipped twice so that it appears to be upside down and
backward.
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Which way does the image move? left to right
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Which way does the image move? The image moves toward you
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Sketch of the "e" with the 4x objective.
Name of specimen: Letter e
Objective used to make drawing: 4x
Estimated size of specimen: app 1400 microns
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Is the field of view larger or smaller with the higher power objective? The field of view gets smaller as
the magnification is increased.
15
Draw the "e" as seen under the 10x objective.
Name of specimen: Letter e
Objective used for drawing" 10x
Estimated size of specimen: 1400 microns
Under the 10x objective, the letter e will take up almost all of the field of view.
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Draw the "e" as it appears under the 40x objective and label.
Name of specimen: Letter e
Objective used for drawing: 40x
Estimated size of specimen: Unable to determine the size. It is not possible to see all of the letter e. Only
small portions of the e are visible.
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As you changed objectives while looking at the "e", did the position of the "e" change? What happened to
the field of view? What happened to the actual size of the specimen?
The position of the letter e should remain the same. The field of view gets smaller as the magnification is
increased. The actual size of the specimen does not change.
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What is the diameter of the 10x field of view in microns? 1500 microns
19
What is the diameter, in microns, of the 40x objective? 375 microns
PROCEDURE: COLORED PAPER
1
How does this compare with the picture as seen with the naked eye? Under the microscope, the piece of
colored paper should appear to be many different colors mixed together.
Make a sketch of the colored paper as it appears under the microscope.
Name of specimen: Colored paper
Objective used: 10x
7 2
What is resolving power (resolution)? For most people, two objects that are less than .1 mm apart cannot
be seen as separate objects by the naked eye. The microscope permits us to detect space between objects
that are much closer than this. However, it can spread the objects so far apart that the picture no longer
makes sense.
3
How can magnification help us? It makes the image appear larger.
4
How can resolution help us? It spreads the image apart so that space can be seen between two objects that
are really very close together.
5
How can too much resolving power be a handicap? It can spread the objects so far apart that the picture no
longer makes sense.
Final Observations
1
Why do you not use the coarse adjustment knob while using the high power objectives?
The coarse adjustment knob moves the stage up and down very rapidly. If the 40 x objective is being used,
moving the coarse adjustment could cause the lens to hit the slide causing damage to the lens.
2
Why must the bottom of slide and the stage be kept dry? If the bottom of the slide is wet, it is difficult to
move the slide around on the stage. The slide will tend to stick to the stage. Also, water under the slide
could distort the image.
3
What is a parfocal microscope? What is the advantage of this?
These microscopes are parfocal. This means that the corresponding focal points on all the objectives are in
the same plane. In other words, if the microscope is focused with one lens, it is in focus on the other lenses.
4
What is the total magnification using the three objectives of your microscope?
The 4x objective has a total magnification of 40.
The 10x objective has a total magnification of 100.
The 40x objective has a total magnification of 400.
5
What is the diameter of the field of view with each objective?
The diameter of the field of view using the 10x objective is 1500 microns.
The diameter of the filed of view using the 40x objective is 375 microns.
I do not have my students measure using the 4x objective.
8 6
Was it easier to estimate the diameter of the letter e using the 10x or 40x objective? Why? Which estimate
do you think is more accurate?
Students should become aware of the fact that it is easier to measure larger items using the 10x objective,
and it is easier to measure very small items using the 40x objective.
7
What three things should always be given with a drawing?
The name of the specimen, the objective that is being used, and the estimated size of the specimen.
8
When first placing a slide on the microscope, what lens should you begin with? How should you proceed
from there?
Always begin with the 4x objective. This is the "scanner" objective. You can quickly scan the entire field
of view. Once you are in focus with the 4x objective, proceed to the 10x objective. You can still use the
coarse adjustment knob to get the specimen into focus. Finally, move the 40x objective into place. Use
only the fine adjustment knob to fine tune the image.
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