HISTORY of the
MICROSCOPE
1590: The first compound
microscope was used
1655 – Robert Hooke used a
compound microscope to
observe pores in cork
He called them “cells”
They reminded him of
prison cells
HISTORY of the
MICROSCOPE
1674 – Anton van Leeuwenhoek
built a simple microscope with
only one lens to examine blood,
yeast, insects and many other
tiny objects.
Compound Microscope
standard microscope
two lenses: ocular lens and objective lens
two or three objective lenses (low, medium, and
high magnification)
Better than magnifying glass, but…
Specimens must be thin so light can pass through
Specimens may need to be stained to see structures
Image viewed is a mirror image of the object
Parts of the
Microscope
Eyepiece
Body Tube
Revolving Nosepiece
Arm
Objective Lens
Stage Clips
Diaphragm
Light
Stage
Coarse Focus
Fine Focus
Base
FUNCTIONS
a.
b.
c.
d.
e.
f.
g.
h.
i.
Magnifies image (10X)
Used for rough focus (use
with low power)
Used for fine adjustments
(use with high power)
Enlarges image (scanning 4x,
low power 10x, high power
40x)
Used for carrying microscope
Platform for holding the slide
Can be a mirror or light bulb
Used for carrying the
microscope
Adjusts the amount of light
Light Compound Microscopes have 3 magnifications:
Scanning: find the object; uses course focus mainly
Low: make clearer
High: only fine focus
Each objective will have written the magnification and the
ocular lens (eyepiece) has a magnification. The total
magnification is the ocular x objective
10x
Magnification
of eyepiece lens
x
4x
=
magnification
of obj. lens
40x
total
magnification
*The greater the total magnification, the
smaller the field of view (FOV) or area
that you see. The lower the total
magnification, the larger the field of view
(FOV).
Microscope Magnification

Calculate the total magnification:
Eyepiece
Lens
Objective
Lens
a. 10x
4x
b. 10x
10x
c. 10x
40x
Total
Magnification
FIELD OF VIEW
-How much can you see?
In High Power we see 25% of the low power FOV
(low power 100 x is 25% of high power 400x)
We see less of the specimen but we see more
details of the specimen under high power
LOW POWER
HIGH POWER
Answer the following Questions
1. After switching from high power to low power
the area of the field of view will appear
a. larger and brighter
b. Smaller and brighter
c. larger and darker
d. smaller and darker
2. What should a student adjust if the field of
view seems too dark?
________________________________
3. Is the field of vision smaller or larger
under low power?
_______________________________
4. To locate and observe a specimen under a slide, a
student should begin by using what objective and what
adjustment knob?
5. What adjustment knob should you use if you are using
high power?
6. Why should a specimen be centered in the middle of the
field of view when focusing under low power?
Microscope Vocabulary
Magnification: increase of an object’s apparent size
Resolution: power to show details clearly
Both are needed to see a clear image
Stereoscopic Microscope
(Dissecting Microscope)
An ocular lens for each eye
Gives a 3-D image
Can view whole organisms
Great for studying external
or surface structure of a
specimen
Images are not reversed
Electron
Microscope
The limit of resolution
restricts the usefulness of
light microscopes for
studying VERY small
specimens such as
viruses.
• Electron microscopes
use a stream of electrons
to view these specimens.
• Electron microscopes
have a limit of resolution
more than 1000 times
finer than light
microscopes.
Electron Microscope: TEM
Best magnification
(250,000 X)
Can see things that
are smaller than a cell
(organelles and
viruses)
Objects must be
thinly sliced and
stained with metal
for viewing
Bamboo
Fiber Cells
Electron Microscope: SEM
Best detail / depth
Less magnification
than a TEM
Able to view a whole
organism and provide
a 3-D image
Foot of House Fly
staple
FIELD OF
VIEW
How do we find the FOV of a
microscope?
Low Power (100x)
1.
2.
3.
Find the diameter of the LP FOV
Use the clear metric ruler (mm
side)
Be sure to line up the first mm
mark with the left side of the
field.
LP FOV = 1.5 mm
The mm is too
large to
measure
microscopic
objects, so you
need to use the
micron
(micrometer)
µm
1 mm = 1,000 µm
1 µm = 1/1000 mm or 0.001mm
LP FOV = 1500µm
So how do we
determine how big
something is in the
microscope?
Let’s see how it works:
Use the following
formula:
FOV
# of cells
(that can fit across
diameter)
FOV = 2mm = .5mm
# of
4
cells
OR .5mm x 1000
=500 microns
CARRYING THE MICROSCOPE
A
B
FOCUSING
1. Always start with the SCANNING
objective.
Odds are, you will be able to see something
on this setting.
Use the Coarse Knob to focus
then the fine adjustment knob until
clear, image may be small
**Do not use stage clips, try moving the
slide around until you find something.
2. Once you've focused on Scanning, switch to Low
Power.
Use the Coarse Adjustment Knob to refocus
Use the Fine Adjustment Knob to make the image
crystal clear
*If you haven't focused on this level, you will not be able
to move to the next level.
3. Now switch to High Power. (If you have a thick slide, or
a slide without a cover, do NOT use the high power
objective).
ONLY use the Fine Adjustment Knob to focus specimens.
DRAWING SPECIMENS
1. Use pencil - you can erase and shade areas
2. All drawings should include clear and proper labels (and
be large enough to view details). Drawings should be
labeled with the specimen name and magnification.
3. Labels should be written on the outside of the circle.
The circle indicates the viewing field as seen through the
eyepiece, specimens should be drawn to scale - ie..if your
specimen takes up the whole viewing field, make sure your
drawing reflects that.
TROUBLESHOOTING
Occasionally you may have trouble with working your microscope. Here
are some common problems and solutions.
1. Image is too dark!
Adjust the diaphragm, make sure your light is on.
2. There's a spot in my viewing field, even when I move the slide the
spot stays in the same place!
Your lens is dirty. Use lens paper, and only lens paper to carefully clean
the objective and ocular lens. The ocular lens can be removed to clean
the inside. The spot is probably a spec of dust.
3. I can't see anything under high power!
Remember the steps, if you can't focus under
scanning and then low power, you won't be able
to focus anything under high power.
Start at scanning and walk through the
steps again.
4. Only half of my viewing field is lit\
You probably don't have your objective fully clicked into place..
TROUBLESHOOTING
Occasionally you may have trouble with working your microscope. Here
are some common problems and solutions.
1. Image is too dark!
Adjust the diaphragm, make sure your light is on.
2. There's a spot in my viewing field, even when I move the slide the
spot stays in the same place!
Your lens is dirty. Use lens paper, and only lens paper to carefully clean
the objective and ocular lens. The ocular lens can be removed to clean
the inside. The spot is probably a spec of dust.
3. I can't see anything under high power!
Remember the steps, if you can't focus under
scanning and then low power, you won't be able
to focus anything under high power.
Start at scanning and walk through the
steps again.
4. Only half of my viewing field is lit\
You probably don't have your objective fully clicked into place..
OTHER TOOLS
Metric Ruler: Length (meters)
M
D
V
Graduated Cylinder: Volume (g/mL)
To read the volume, you must look at the bottom of the
_____________ which is a curve surface.
Triple Beam Balance: Mass (grams)
OTHER TOOLS
a magnifying glass
One lens
Low magnification and low resolution
OTHER TOOLS
Centrifuge- technique used to separate substances based on
density
Spins material at very high rates of speed
Materials suspended in a liquid are spun around very rapidly.
Heaviest particles settle at bottom; lightest particles
settle on top.
OTHER TOOLS
Spectrophotometer
Measures amount and kind of light absorbed by a material.
Spectrophotometry: is the use of light to analyze samples.
OTHER TOOLS
Chromotography- technique used to separate
substances based on their chemical make up
( the different colors of leaves are
separated this way)
A family of techniques for the separation of mixtures.
Separates different substances from each other on the
basis of their chemical or physical properties
Be familiar with paper chromatography
OTHER TOOLS
Gel electrophoresis -technique used to separate substances
based on their electrical charge.
(DNA is separated this way)
Separates substances based on size and electrical charge
An electrical current is run through a gel that contains the
substance being studied
Different components of the substance move at different
rates through the gel