Parts of the Compound Light
Microscope
Slide # 2
Microscope Parts and Functions
A
M
L
B
C
K
J
D
I
E
H
G
F
A. Eyepiece: Holds ocular
lens; lens that you look
through; magnified image
of objective lens
B.
Arm: supports tube &
connects it to the base
C. Stage Clip: holds
microscope slide in place
D. Coarse adjustment:
raises / lowers stage to
bring image into focus
E. Fine adjustment: brings
image into sharp focus
F. Base: Supports
microscope
G. Illuminator: Light source
Slide # 3
Microscope Parts and Functions
A
M
L
B
C
K
J
D
I
E
H
G
F
H. Diaphragm: Controls
the amount of light that
passes through a
specimen
I. Stage: platform that holds
the slide
J. Microscope slide: holds
the specimen
K. Objective lenses:
magnifies the specimen
– Shortest lens has least
magnification
– Longest lens has
greatest magnification
Slide # 4
Microscope Parts and Functions
A
M
L
B
C
K
J
D
I
E
H
G
F
L. Revolving nosepiece:
holds 2 or more objective
lenses
M. Body tube: Connects
eyepiece to objective lens
Slide # 5
How to Calculate Magnification
Magnification of eyepiece X magnification of
objective lens
If eyepiece is 10 x and objective lens is 4x, then what is the total
magnification?
10x X 4x = 40X
Slide # 6
TAKS PRACTICE
A student wants to view cells under the
compound microscope at a total magnification
of 400X. If the eyepiece is 10X, which of the
following objective lenses should be used?
A 4X
B 10X
C 40X
D 100X
Correct Answer = C
How do we calculate
magnification?
Eyepiece X Objective lens =
Total magnification
10x X n = 400x
10x
= 10x
n = 40x
Slide # 7
How a Light Microscope Works
1. Use lenses to make small objects
appear larger
2. Compound light microscope: Two
lenses separated by a tube
3. Lenses magnify an object by
bending the light that passes
through the lens
4. Magnification: ability to make
things appear larger than they are
5. Resolution: fineness of detail that
can be seen in an image
Go to
Section:
Slide # 8
Microscope Safety
1. Always use 2 hands to carry a microscope; one on
the arm and one hand supporting the base
2. Only use lens tissue to clean lenses
3. When focusing, always look to the side to watch and
make sure the objective lens doesn’t hit the slide
4. Always use the lowest power (shortest) objective
lens for bringing specimen into focus
5. Bring specimen into focus by first using coarse
adjustment, then use fine adjustment
6. Never use a microscope with a frayed cord
7. Because we have running water in our lab area,
NEVER turn on the water when using a microscope
Slide # 9
1.
2.
3.
4.
How to Prepare a Slide
Place slide on a flat surface.
Place a drop of water on the slide. Add the specimen to the drop
of water (at times, you may want to have the specimen already
on the slide before adding the water).
Hold the coverslip by its sides and lay its bottom edge on the
slide close to the specimen. Holding the coverslip at a 45° angle
helps.
Slowly lower the coverslip so that it spreads the water out. If you
get air bubbles (looking like little black doughnuts), gently press
on the coverslip to move them to the edge. If there are dry areas
under the coverslip, add a little more water at the edge of the
coverslip. Too much water can be dabbed off with a piece of
paper towel
Slide # 9
How to Prepare a Slide
The diagram below shows how a cover-slip should be
lowered onto some single-celled organisms during the
preparation of a wet mount.
Why is this a preferred procedure?
A The cover-slip will prevent the slide from breaking.
B The organisms will be more evenly distributed.
C The possibility of breaking the cover-slip is reduced.
D The possibility of trapping air bubbles is reduced.