Name: ___________________
Period: ___________
Partner ___________________
Partner ___________________
Use of the Light Microscope
Possibly the most important instrument that aids biologist is the microscope. A microscope allows
scientist to investigate the world that is otherwise too small to be seen. An opportunity to learn
about the use of this valuable instrument is now yours. A light microscope magnifies objects up to
approximately 400 times their natural size.
Two types of slides are used with the microscope: prepared slides and temporary wet mounts.
Prepared slides are permanent and are made to last a long time. These slides are usually purchased
by the school. Most of the slides you will use in this course will be wet mounts. You will make
these slides yourself. As the name temporary wet mount suggests, these slides are not permanent.
In this investigation, you will
a.
practice proper handling of the light microscope
b.
learn the names and functions of the light microscope parts.
c.
acquire skill in using the light microscope by carefully following all directions.
d.
prepare a wet mount of an “e”.
e.
locate objects under low and high power magnification
Materials
Light microscope
Microscope slide
Coverslip
Tweezers
Preserved “e”
Water
Dropper
Scissors
News print
____________________ Taken and passed microscope quiz with 90%+.
(Dr. Smoot’s signature)
Procedure
Part A Learning microscope Parts and Functions
Look at Figure 1. Note that the student is carrying
the microscope with two hands. Also note that the
microscope is carried straight up. Do not tilt or tip the
microscope as you carry it with both hands close to
the body
A mirror is attached to most microscopes by means
of a swivel joint. Position the concave surface (curved
surface) of the mirror so that it is turned toward a light
source, such as ceiling lights windows in the room, or
a desk lamp. A lamp may be built into your
microscope. This lamp replaces the mirror and
outside light source. CAUTION: Never use direct
sunlight as a light source. Direct sunlight will
damage your eyes.
Look at Figure 2. Use the diagram that looks most like your microscope to locate
microscope parts
1.
Does your microscope have a lamp or a mirror?
__________________________________________________________________
2.
What type of diaphragm does your microscope have?
__________________________________________________________________
A diaphragm controls amount of light entering the microscope. Turning the
diaphragm adjust the amount of light passing through the microscope. (iris
diaphragm or revolving)

Use Figure 2 to help you locate the revolving nosepieces, high power objective,
and low power objective on your microscope.
The low power objective is identified by a “10X”
marking or by its short length.
The high
power objective usually has a “43X” marking and
often is longer than the low power objective.
The objectives can be changes by turning the nose
piece (Figure 3).
Stop and place a check mark in the square next
to each part of the microscope you can locate:
diaphragm
lamp or mirror
revolving nosepiece

high power objective
low power objective
Use Figure 2 to help you locate the eyepiece, coarse wheel adjustment, fine
adjustment, stage, and stage opening on your microscope.

Stop and place a check mark in the square next to each part of the microscope you
can locate:
 eyepiece
 stage
 coarse wheel adjustment
stage opening
 fine wheel adjustment
_________Dr. Smoot’s initials
PART B. USING THE MICROSCOPE

Turn on the lamp or position the mirror toward the light source

Turn and click the low power objective so that it is directly over the stage
opening. An objective is in proper viewing
position when directly over the stage opening. Most
microscopes will “click” when the objective is in
viewing position.

Look through the eyepiece of the microscope.
circle of bright light should now be visible. Keep both
open. Keeping both eyes open will reduce eyestrain.

Adjust the mirror and diaphragm to make the
of light as bright as possible.
proper
A
eyes
circle

Look to the side of the microscope as
shown in Figure 4. Slowly turn the coarse
wheel adjustment back and forth. DO NOT
force the wheel once it stops.
When
the wheel stops, turn it in the opposite
direction. Note the movement of the low
power objective in relation to the stage.
3.
In which direction does the objective
move as your turn the coarse wheel
adjustment toward you?
________________________
4.
In which direction does the objective
move as you turn the coarse wheel
adjustment away from you?
______________________________
The eyepiece contains a glass lens which
magnifies 10 times (10X). The low power objective also contains a lens which magnifies 10
times (10X). Therefore, the total magnification of an object when viewed under low power is
100X. Total magnification under low power is calculated by multiplying the magnification of
the low power objective (10) by that of the eyepiece (10). The total magnification of an object
when viewed under high power is calculated by multiplying the magnification of the high power
objective (usually 43) by that of the eyepiece (10).
5.
What is the total magnification of your microscope under low power? (Use the
numbers printed on your low power objective and eyepiece if present.) ________
6.
What is the total magnification of your microscope under high power? (Use the
numbers printed on your high power objective and eyepiece). _______________
The objectives and eyepiece should be cleaned with lens paper at the beginning of each
laboratory period. Always use lens paper to clean lenses. Other type of paper may scratch or
smear lenses.
 Clean the objectives and eyepiece of your microscope using lens paper. Use one piece of
paper and gently wipe each lens.
___________________
Dr. Smoot’s initials showing you have done the previous steps.
PART C. PREPARATION OF A TEMPORARY WET MOUNT.
A temporary wet mount consists of some object places in a drop of water on a slide with a
coverslip over the object. Use the following steps in preparing your wet mount.
 Step 1. Add a small drop of water
to slide as shown. Figure 5A.
 Step 2 Place the object to be
viewed in the water drop. (If
available from Investigation 1, use
one leg only from one of the insects
collected.)
 Step 3 Use probe to position a coverslip as shown in Figure 5B. Use of probe avoids
fingerprints on the coverslip.
 Step 4 Lower the edge of the coverslip down slowly over the water drop and object.
procedure will prevent trapping air under the coverslip
getting
This
PART D LOCATING AN OBJECT UNDER THE MICROSCOPE
 Click the low power objective into viewing position. NOTE: Always locate an object first
with low power magnification even if a higher magnification is desired.
You should not have to turn the adjustment
all the way either direction.
If you are having difficulty raise your hand and wait for Dr.
Smoot
 Adjust the diaphragm and mirror for the best light.
 Place the wet mount of the “e” on the stage of your microscope. Position the slide on the stage
so the “e” is directly over the center of the stage opening. Secure the slide in place with the
clips.
 Look to the side of your microscope as shown in Figure 4. Slowly lower the low power
objective by turning the coarse wheel adjustment until the objective almost touches the glass
slide. Some microscope slides have an automatic stop which prevents lower the objective onto
the slide. Other microscopes do not. CAUTION: Never lower the objective toward the stage
while looking through the eyepiece.
 While looking through the eyepiece with both eyes open, slowly turn the coarse wheel
adjustment so the objective rises or moves away from the stage. The “e” should become visible.
 Bring the “e” into sharp focus by turning the fine wheel adjustment.
PART E. INCREASING THE MAGNIFICATION OF THE MICROSCOPE
 Any object to be viewed under high power magnification is always located first under low
power and focused. Locate and center the “e” under low power of your microscope.
 Move the low power objective out of viewing position. Look to the side of the microscope and
revolve the nose piece (Figure 3). Click the high power objective into viewing position.
Look through the eyepiece. The “e” should be
visible. However, it may need to be focused.
Use the fine adjustment wheel only to sharpen
the focus. CAUTION: Never use the coarse
wheel adjustment for focusing with high power.
Damage to the lens and slide may result if the
coarse adjustment is used.
If you are unable to find the “e”, then do the
following. While looking through the eyepiece,
move the glass slide slightly to the left, right
away from, or toward you. These movements may help to reposition the “e” directly in the
center of the high power objective.
Repeat Parts D and E if you are unable to locate the objective under high power.
 Draw a picture of what you see under the microscope in the circles below, one with low power
and one with high power. Fill the circle.
Drawings of “e”.
Low Power
High Power
Analysis
1.
Match the microscope parts listed in Column I with their correct function in Column II.
Place your answers along the left side of Column I.
Column I
_______ diaphragm
_______ stage opening
_______ mirror or lamp
_______ eyepiece
_______ low power objective
_______ high power objective
_______ revolving nosepiece
_______ coarse adjustment knob
_______ fine adjustment knob
_______ stage
_______ stage clips
Column II
a. allows light to pass through stage
b. brings objects into rapid but coarse focus
c. regulates amount of light entering scope
d. is attached to revolving nosepiece and contains a
lens capable of 10X magnification
e. holds glass slide and specimen in place
f. supports slide
g. directs light into scope
h. turns to change from one power to another
i. contains a lens capable of 10X magnification
j. brings objects slowly into fine focus
k. contains a lens capable of 43X magnification
2. Answer the following statements as true
or false. If it is false, correct it.
a. Total magnification of a microscope is determined by adding the eyepieces lens
magnification to the objective lens magnification. ____________________
b. An object should always be located first with low power. __________________
c. A light microscope should be carried in an upright position with both hands. _______
d. The fine wheel adjustment must be used to sharpen focus when using high power
magnification ______
e. Always look to the side of a light microscope when lowering the objective. ________
f. Paper towels or newspaper may be used to clean the lens of a microscope. _________
g. If the eyepiece of a microscope is marked 10X and the high power objective is marked
50X, the total magnification is 500X. __________
Required second specimen
Low Power
High Power
Required third specimen
Low Power
High Power
Additional specimens
Low Power
High Power
Low Power
High Power