The Microscope
Why do we use a microscope?
• Many things are smaller than we can see
with the naked eye. To accurately study
Biology we need a tool to help us see
these tiny things.
History
• Antony van Leeuwenhoek is credited with
developing the first microscope in about 1665.
Although the compound microscope was already
in use, what made Antony’s invention special
was that he was able to magnify his ‘wee
beasties’ by up to 270X.
• Antony was the first to see bacteria, red blood
cells, yeast and so much more!
Types of Microscopes
• Binocular scopes allow you to see in 3D.
• Binocular Compound Microscope
– A compound microscope is one that has two
lens, usually one in the eyepiece and another
that can be varied.
– These have a magnification of up to 1000X.
– We use binocular scopes in our lab.
• Stereo Microscope
– A stereo microscope has a magnification of
about 10 X.
– With a stereo microscope you can look at the
details of larger objects. For example, an
entire leaf or the whole body of a spider.
• Monocular Compound Microscope
– A monocular microscope has just one
eyepiece to look through.
– Most students find this type of scope more
challenging to use.
Electron Microscopes
• Objects smaller than 0.2 um can be seen
with an electron microscope. (Viruses,
internal cellular structures)
Scanning Electron Microscope
• Scanning Electron Microscope
– Image appears in 3-dimensions and in
black and white.
• The magnification is usually 1000X to
10,000X.
• It is particularly useful for studying the
surfaces of cells and viruses.
Scanning Electron Microscope
Weevil, 75X Mosquito head, 200X
Red blood cells, color enhanced
Transmission Electron Microscope
• The item to be viewed is sliced into very
thin slices, the image is a slice of the cell.
• These images are used to cross sections
of cells and their intracellular structures.
• Magnification can be as much as 10,000X
to 100,000 X.
Sperm cross section TEM,
Mycobacterium tuberculosis TEM
Know the following Microscope
parts and their function.
•
•
•
•
•
•
•
•
Eyepiece
Ocular lens
Nosepiece
Objective lens
Stage
Stage clip
Light switch
Light intensity knob
•
•
•
•
•
•
•
•
Fine adjustment
Coarse adjustment
Stage manipulator knobs
Condenser
Light source
Iris diaphragm knob
Cord holder
Microscope body
Ocular Lens
• The ocular lens has a 10X magnification.
Objective Lens
• There are four objective lenses.
•
•
•
•
Red – 4X
Blue – 10X
Yellow – 40X
Oil immersion (white) – 100X
Total Magnification
• When the image
travels through
the objective
lens and the
ocular lens it
magnifies the
magnification of
the objective
lens by 10X.
Ocular
lens
Objective
lens
Total
magnification
10X
Red
4X
40X
10X
Blue
10X
Yellow
40X
White
100X
100X
10X
10X
400X
1000X
The proper way to carry your
microscope.
• Always carry the
microscope with two
hands, holding it
close to your body.
Improper carrying.
• Carrying the
microscope like this
could result in your
ruining a $1500.00
piece of equipment.
• This will not score you
brownie points with
your instructor!
Proper usage
• At the lab table, unwrap
only as much cord as you
need, the rest should
remain stored around the
cord wrap.
• The microscope
should always be
stored with the 4X
(red) lens in place
and the stage in its
lowest position.
• Always store your
microscope in its
numbered position,
with the dust cover in
place.
How to focus your image
• Place the slide on the stage, held in place by the
stage clip.
• ALWAYS start with the 4X lens. Focus your image.
• Move to the 10X lens, focus.
• NEVER use the coarse focus higher than 4X.
• Repeat at the 40X lens, focus using the fine focus.
Distance between lens and slide
• Use only the fine
focus knob with the
40X and 100X lens.
The Oil Immersion Lens
• The oil immersion lens or 100X lens is
used with special optical oil. It makes the
image clear at a higher magnification
• Your instructor will tell you if you need to
use this lens.
• It is important to remove all the oil if you
use the oil immersion lens.
Cleaning
• Please use only lens paper to clean the
lenses, never paper towels or Kimwipes.
• Never use dry lens paper to clean
eyepieces. Use the cleaning solution
provided or breathe on the surface to be
cleaned, then wipe.