The Microscope
8th Grade Science
2009
Miss Lorenson
The Compound Light Microscope
–Has two magnifying lenses
• ocular
• objective
–Uses light for viewing
–Most common used scope
Parts of a Microscope
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When carrying a microscope
always use both bands
• One hand under the base
• One hand holding the arm
• Carry the microscope
close to your body
Knobs
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Turning the Light On
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Magnification
• To determine the TOTAL magnification
of a microscope multiply the
magnification of the two magnifying
lenses…
Ocular X Objective = Total Magnification
Ocular Remains the Same
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Objectives Rotate in Nosepiece
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Each Microscope has 3 or 4
objectives on it.
Each objective has its
magnification written on it.
We will use three objectives in
this class.
Scanning Objective (4x)
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Total Magnification =
10 (ocular)
X
4 (objective)
Low Power Objective (10x)
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Total Magnification =
10 (ocular)
X
10 (objective)
High Power Objective (40x)
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Total Magnification =
10 (ocular)
X
40 (objective)
Powers of Magnification
Lens
Magnification
Objective
Magnification
10x
4x
5x
40x
10x
44x
Total
Magnification
Key Terms
• Field of View (field)
– Lighted circle seen
when looking
through the ocular.
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• Depth of Focus
– On higher
magnification not
everything in field
will be in sharp focus
- objects in different
layers.
The Art of Focusing
• Use the arms on the stage to hold slide in
place.
• Always begin with the Scanning Objective!
• Use the course adjustment knob to get
maximum working distance.
• Look through the ocular at all times.
• Once the field is in focus with the scanning
objective then you can rotate to the low
power (10X) objective, make sure the
objective NEVER touches the slide.
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QuickTime™ and a
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• When finished viewing
the slide maximize
working distance and
remove the slide from
the stage.
• To view another slide
start on the scanning
objective and repeat the
focusing process.
• When finished for the
day clean the
microscope slides
(temporary)
• Turn off light.
• Unplug the
microscope
• Coil the electrical
cord
• Return to
appropriate space or
box
Temporary Wet Mount Slide
1. Place specimen on the center of the
slide.
2. Add a small drop of water on top of the
specimen.
3. Use tweezers to place the coverslip on
top of the water drop.
4. Slowly lower it down on the slide on
one side to make sure you don’t have
air bubbles.