Microscopes

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Microscopes

• Biology 11

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The History

• Many people experimented with making microscopes
• Was the microscope originally made by accident?
  (Most people were creating telescopes)
• The first microscope was 6 feet long!!!
• The Greeks Romans used lenses to magnify
  objects over 1000 years ago.

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The History

• Hans and Zacharias Janssen of Holland in the
  1590s created the first compound microscope

• Zacharias Jansen
• 1588-1631

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The History

• Anthony van Leeuwenhoek and Robert Hooke made
  improvements by working on improving the lenses

Robert Hooke 1635-1703
Anthony van Leeuwenhoek 1632-1723
Hooke Microscope
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How a Microscope Works
Convex Lenses are curved glass used to make
microscopes (and glasses etc.)
Convex lenses bend light and focus it in one spot.
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How a Microscope Works
Objective Lens (Gathers Light, Magnifies And
Focuses Image Inside Body Tube)
Ocular Lens (Magnifies Image)
Body Tube (Image Focuses)

• Bending Light The objective (bottom) convex lens
  magnifies and focuses (bends) the image inside
  the body tube and the ocular convex (top) lens
  of a microscope magnifies it (again).

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The Parts of a Microscope
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Ocular Lens
Body Tube
Nose Piece
Arm
Objective Lenses
Stage
Stage Clips
Coarse Adjustment
Diaphragm
Fine Adjustment
Light Source
Base
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Body Tube

• The body tube holds the objective lenses and the
  ocular lens the proper distance apart

Diagram
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Nose Piece

• The Nose Piece holds the objective lenses and can
  be turned to choose a different magnification
  objective.

Diagram
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Objective Lenses

• The Objective Lenses increase magnification
  (usually from 4x to 40x)

Diagram
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Stage Clips

• These 2 clips hold the slide/specimen in place on
  the stage.

Diagram
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Diaphragm

• The Diaphragm controls the amount of light on the
  slide/specimen

Turn to let more light in or to make dimmer.
Diagram
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Light Source

• Projects light upwards through the diaphragm, the
  specimen and the lenses
• Some have lights, others have mirrors where you
  must move the mirror to reflect light

Diagram
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Ocular Lens/Eyepiece

• Magnifies the specimen image

Diagram
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Arm

• Used to support the microscope when carried.
  Holds the body tube, nose piece and objective
  lenses

Diagram
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Stage

• Supports the slide/specimen

Diagram
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Coarse Adjustment Knob

• Moves the stage up and down (quickly) for
  focusing your image, use only with low power
  objective lens!

Diagram
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Fine Adjustment Knob

• This knob moves the stage SLIGHTLY to sharpen the
  image

Diagram
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Base

• Supports the microscope

Diagram
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Label the microscope diagram

• Page 627 in the textbook will help

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Parts of a microscope
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What the parts do

1. the lens you look through, magnifies the specimen
2. supports the microscope
3. holds objective lenses
4. magnify the specimen (2)
5. supports upper parts of the microscope, used to
   carry microscope
6. used to focus when using the high power objective
7. where the slide is placed
8. regulates the amount of light reaching the object
9. used to focus when using the low power objective
10. provides light
11. hold slide in place on the stage

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Caring for a Microscope

• Carry it with 2 HANDSone on the arm and the
  other on the base.
• Make sure its on a flat surface, away from the
  edge of the desk.
• Dont pull on the cord to unplug it.
• Clean lenses only with lens tissue.

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Carry a Microscope Correctly
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Using a Microscope

• Start on the lowest magnification, with the stage
  lowered.
• Place slide on stage and lock with clips.
• Use coarse adjustment knob to center the sample
  and focus on the object.
• Adjust light source using the diaphragm.
• Use fine adjustment to focus.

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Using a Microscope (contd)

• Rotate the nosepiece to increase magnification
  from lowest to highest.
• Use only the fine adjustment knob to focus on
  high power.

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Microscopy involves 2 processes

• Magnification
• enlargement
• Resolution (resolving power)
• - sharpness of the image

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Magnification

• The ability to increase the size of the image of
  a specimen.
• Total magnification of an image is found by
  multiplying the power of the ocular lens by the
  power of the objective.
• The larger the magnification the less area you
  are able to see.

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Resolution

• The ability to see details clearly.
• in order for the increased magnification of a
  microscope to be of use, its resolution must also
  be increased
• resolution is dependant on the quality of the
  lens and is limited when using light microscopes

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Microscope video.

• Fill out response while you watch.

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Simple Microscope

• Anton van Leewenhoek was the first to use the
  single lens microscope for biological purposes.
• Consisted of a single lens
• used today for quick observations in the field
• specimens may be alive for examination.
• but it has low magnification

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Compound Light Microscope

• Consists of two lenses, the ocular and the
  objective, both of which magnify the image
• these two lenses form the optical system.
• Structural parts that hold the specimen and the
  lenses is called the mechanical system

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Compound Light Microscope

• Uses
• good for basic lab work (up to 1500x)
• can be used to view living things but most
  specimens are dead
• usually used with stain
• Disadvantages
• cannot view cell structures
• low resolution

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Stereo microscope (dissection)

• Two sets of lenses- an ocular and an objective
  for each eye
• Uses
• allows the scientist to view images as 3-D
• used to study external structures and for
  dissections
• specimens may be kept alive for examination.
• Disadvantage
• Low magnification (6-50x)

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Phase Contrast (lens) Microscope

• Changes the way light passes through a living
  specimen with phase plates
• Can see cell structures that are not usually
  visible under a compound microscope.
• Useful for examining live specimens
• But has a low magnification

Frits (Frederik) Zernike won the Nobel prize 1953
for the development of this microscope.
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Transmission Electron Microscope

• Electron beam is sent through a vacuum chamber
  then electromagnets focus the image on a screen
• an image can be magnified a million times so you
  can see cell structures and specimens smaller
  than a cell
• Vacuum is needed, specimens are dead and required
  complex procedures to prepare them

Also know as the TEM
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Scanning Electron Microscope

• Like the TEM, this microscope uses electrons to
  focus an image and is able to view things much
  smaller than the light microscope.
• Unlike the TEM, the SEM allows the viewing of 3D
  images and has better resolution.
• Vacuum is needed, specimens are dead and required
  complex procedures to prepare them. Lower
  magnification possible

Also known as the SEM
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Scanning electron micrograph (SEM) of various
Pollen. Public domain image reference Dartmouth
Electron Microscope Facility, Dartmouth College
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Microscope Calculations