Microscopy

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Microscopy
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COMPARING LAB AND ELECTRON MICROSCOPES

• Much higher magnification and superior
  resolution can be obtained using the ELECTRON
  MICROSCOPE. Most of the descriptions of the cell
  in your textbook are based on information
  obtained with transmission electron microscopy
  (TEM).
• ITEM LIGHT MICROSCOPE
  ELECTRON MICROSCOPE
• Illumination
• Source LIGHT
  
  ELECTRONS
• Lenses CONDENSER LENS,
  PROJECTOR, OBJECTIVE--
• Present SAME ON BOTH, BUT
  DIFFERENT POSITIONS AND
• ELECTROMAGNETIC COILS ON ELECTRON
  MICROSCOPE
• Specimen ON GLASS SLIDE
  ON SPECIAL HOLDER
• Stage Location BOTTOM, HOLDS SLIDE
  BOTTOM, PROJECTS IMAGE
• Vacuum
• system USES
  AIR/OIL VACUUM
• Can you guess the reason the light microscope is
  named light microscope?

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Functions of the parts of the microscope

• Diopter ring adjusts focus for left eye
• Revolving nosepiece rotates objectives
• Objective magnified image
• Mechanical stage hold specimen
• Iris diaphragm adjusts light coming in
• Interpupillary distance adjusts for width of
  eyes
• Coarse adjustment knob adjusts coarse focus
• Fine Adjustment knob adjusts fine focus
• Stage control knob moves stage sideways
• Rheostat adjusts light intensity

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Iris diaphragm (adjusts light coming in)
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(No Transcript)
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OBJECTIVES

• Ocular 10x
• Scanning 5x
• Low Power 10x
• High Power 45x

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TOTAL MAGNIFICATION

• Multiply the ocular magnification (10x) by the
  objective magnification
• For scanning, 10 x 5 50
• For LP, 10 x 10 100
• For HP, 10 x 45 450

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WORKING DISTANCE

• The distance between the slide and the objective.
• Working distance decreases with increasing power.

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FIELD DIAMETER

• Field diameter is the circle that you see when
  you look in the microscope.
• Field diameter decreases with increasing power.

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HOW TO PREDICT THE FIELD DIAMETER OF AN OBJECTIVE

• FD unk obj FD known obj x TM known
  objective
• -----------------------
  --------------------------
• TM unknown
  objective

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Example

• If a scanning objective (5x) has a FD of 4mm,
  what is the FD of an objective whose total
  magnification is 100?

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ANSWER

• FD unk obj 4 x 50
• -------------
• 100
• FD unk obj 2
• Then multiply by 1000 to convert to microns
• ANSWER 2000 microns

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Sample Problems

• If there are 5 cells across a field diameter of
  3500 microns, how wide is each cell?
• 3500 divided by 5 equals 700 microns.
• Each cell is 700 microns wide.

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Sample Problems

• If there are six cells across a field diameter
  and each cell is 700 microns, what is the field
  diameter?
• 700 x 6 4200
• The field diameter is 4200 microns.

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RESOLUTION

• As magnification increases, resolution IMPROVES,
  but the RESOLUTION NUMBER DECREASES.