Download The Compound Microscope

Microscopes
Viewing the Unseen
World
Microscopes
Devices that produce magnified
images of structures that are too small
to see with the unaided eye.
Types of Microscopes
- Compound Microscopes
- Stereo or Dissecting Microscopes
- Electron Microscopes
The Compound
Microscope
-Produces a magnified image
by focusing visible light rays.
-Uses 2 lenses
-Can observe living or
nonliving specimens.
-Magnification is limited by
visible light.
The Stereo or Dissecting Microscope
• The Stereo
Microscope is used
when viewing large
specimens.
• A 3-D image is
viewed.
• Light does not pass
through object but
magnifies the surface.
The Electron Microscope
• -This type of microscope
focuses beams of electrons to
magnify an image.
- It magnifies 1000X or more
than a compound light
microscope.
-It cannot be used to study live
specimens because they must
be dried and in a vacuum inside
the microscope
Quick Questions:
Q: What are 3 types of microscopes?
A: Compound, Dissecting (stereo) and electron
Q: Which allows light to pass through a specimen?
A: Compound microscope
Q: Which does not allow light to pass through a
specimen?
A: Dissecting or stereo microscope
Q: Which uses electrons and a computer to interpret
the results?
A: electron microscope
3 types of electron microscopes
• Scanning Electron Microscope – SEM
• Produce a realistic, 3D image- but only the
surface can be observed. Magnifies 60,000x
• Transmission Electron Microscope – TEM
• 2D images used to study details of cells.
Magnifies 100,000+ X
• Scanning Tunneling Microscope – STM
magnifies so much that scientists can see
atoms on the surface of objects. Magnifies
100 million X
The Compound
Microscope
Essential Questions:
What are the parts of a
compound microscope, and
what function does each
serve?
Eyepiece (Ocular)
The Eyepiece(Ocular)
The lens system in microscope that is nearest your eye. It magnifies the image formed by the objective.
• Part of the
microscope you
hold your eye up to
and look through.
• The eyepiece
contains a
magnifying lens
and magnifies 10X.
360 –Degree
Rotating Head
• The head is able
to rotate 360
degrees without
moving the base
of the
microscope and
disturbing the
focus.
The Revolving
Nosepiece
• Holds three or four
objective lenses.
• The nosepiece can be
rotated to change the
objective lens being
used.
• Each objective lens
has different level of
magnification
The Objectives
• Primary magnification of
the object being viewed.
• Inscribed on each
objective is the
magnification of the lens.
4X – scanning lens
10X – low power
40X – high power
Note: We will NOT be using
100X objective lenses in
this class
Total Magnification
• To find total magnification MULTIPLY the
number on the objective lens times the
number on the eyepiece.
Quick Question:
Q: What would be the total magnification if I was looking
through the ocular lens and using the scanning lens (4X)?
A: 10 X 4 = 40
Q: What would be the total magnification if I was looking
through the ocular lens and using the low power lens
(10X)?
A: 10 X 10 = 100
Q: What would be the total magnification if I was looking
through the ocular lens and using the high power lens?
A: 10 X 40 = 400
The Arm
• The main vertical
section supporting a
microscope
• One hand is
ALWAYS placed on
this when carrying the
microscope!
The Stage
• Platform that supports
the slide
• This is where you
place a sample that
you are trying to view
• It should ALWAYS
be lowered completely
when placing a sample
on it
The Stageclips
• Holds a slide in
place as it is being
observed.
The Diaphragm
• The Diaphragm is a disc
located under the stage.
• It contains 5 or 6 holes to
control the amount of light
that passes up through the
specimen
• This is the most underused
piece of equipment on the
whole thing.
• Too much light washes
out the details of the
specimen
Quick Question:
Q: What is the most underused piece of equipment
on the microscope?
A: The Diaphragms
Q: What does it do?
A: regulates the amount of light being passed
through a specimen
Q: If you use it wrong, what happens?
A: They specimen gets “washed out” and you loose
the fine details such as organelles, cilia, and
flagellum
The Illuminator
(Light Source)
• Light source
for the
Microscope
The Base
• The Base supports the
microscope.
• This is where your
other hand goes when
carrying a microscope
• You hold the base
with one hand and the
arm with the other
hand.
Quick Question:
Q: What is the ONLY way that you will
EVER carry a microscope in my class?
A: With BOTH hands; one on the arm, the
other under the base
Focusing Knobs
• The Course Adjustment Knoblarger and is used to focus the
image.
– This is what you use to lower the
stage prior to placing a specimen
on it
– Only used with the scanning lens
• The Fine Adjustment Knobsmaller and is used to sharpen
the image.
– Fine tuning once you get close
Magnification:
The Microscope’s job is to enlarge
images
Unfortunately, as we increase magnification, we decrease
Resolution, which is how clear something looks
Magnification vs. Resolution
• Magnification is the process of enlarging an
image
• Resolution the level of clarity or detail that
is evident
• Example: Take a picture on your cell phone,
then blow it up on your computer screen
• What happens?
Now for some Practice
• Get with a lab partner at one of the stations
around the room.
– ALWAYS make sure that chord is unwound
from around the microscope, and plugged into
an outlet.
– Turn the power switch ON when using, and
OFF when you are done!
Preparing a sample – do as I do
•
•
•
•
Take a glass slide from the bench
Place a sample on the slide using a pair of forceps
Place a SINGLE drop of water on the sample
Take a cover slip from the bench, and DO NOT
touch anything except the sides (they smudge
easily)
• Place the cover slip at a 30° angle to the sample
on the slide, and gently drop it onto the drop of
water over the sample
Next…
• Lower the Stage ALL THE WAY using the
Coarse Adjustment knob.
• Place the sample on the Stage, under the
stage clips.
• Make sure that the Revolving Nosepiece is
turned to the scanning lens (4X)
Now for the finishing touches…
• Look through the Ocular Lens, and
SLOWLY raise the Stage by using the
Coarse Adjustment Knob until you start to
see an image
• As soon as you see SOMETHING, switch
to the Fine Adjustment Knob, and continue
raising the Stage until your image is in view
• Move the slide gently to center the image
Once your image is in view…
• Rotate the Revolving Nose Piece to the next
higher lens (Low power; 10X) and make sure your
image is still centered
• Use the Fine Adjustment Knob ONLY from now
on
• Refocus the image, and Make sure it is centered.
• What do you notice about your movement of the
slide versus how the image moves?
Last Time…
• Now rotate your revolving nosepiece again to
the high power lens (40X), and focus one more
time using the fine focus knob ONLY!
• What do you see?
• Now adjust the diaphragm while looking
through the ocular lens and see what happens to
the details of your sample
• Stick with the one that has the greatest detail
The finishing touches…
• In many cases you will be asked to draw or
document what you view under a
microscope
• This is how it is to be done, NO OTHER
WAY!
Draw a large circle on a sheet of paper,
if there isn’t already one given to you
1.
2.
Circle
Title the top with what the
image is
3. Record the magnification
4. Diagram what you see at the
HIGHEST
MAGNIFICATION you get
clearly
1.
You may need to do different
sketches at different
magnifications for the same
sample at times
Letter e
400 X
Now it’s your time to try…
• Now that you have the image and it is recorded, pick a partner to go
first
• That partner is to select a sample, prepare a slide, and place it on the
microscope.
• Next, mis-adjust several settings WITHOUT causing damage to the
microscope
• Now stand back and watch as your partner fixes it, and gets the image
into the correct magnification and focus, and draws it on their practice
sheet.
• Once they have it correct, they may select a sample, prepare it, and
mis-adjust the scope.
• Continue until both partners are comfortable with finding images in
the microscope.