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					   Chapter 3
Section 1 Microscopes
Units of Measure
 Metric system of measurement
   International System of Measurement SI
 Base Unit is the Meter (m)
     Kilometer = 1,000 m (2/3 of a mile)
     Centimeter = .01 m (1/2 diameter of penny)
     Millimeter = .001 m (width of pencil tip)
     Micrometer = .000001m (bacteria cell)
     Nanometer = .000000001 m (water mol.)
Light Microscopes
               Light passes through
                one or more lenses
                to produce an
                enlarged image of a
                specimen
Electron Microscopes
               Forms an image of a
                specimen using a
                beam of electrons
                rather than light
               3 Types
                  Transmission electron
                   microscopes (TEM)
                  Scanning electron
                   microscope (SEM)
                  Scanning tunneling
                   microscope
Micrographs
               The image produced
                by the microscope
                  Type of microscope
                  Magnification
                  Name of object
               Light Microscope
               320 magnification
               Amoeba
Magnification & Resolution
 Magnification
   Makes the image appear larger than its
    actual size
 Resolution
   A measure of the clarity of an image
 High magnification & good resolution are
  needed to view details of extremely small
  objects clearly.
Limitations of Microscopes
 Light microscopes: lower magnification
  power but can view LIVING cells
 Electron microscopes: higher
  magnification but cannot view living cells
Light Microscope
               Ocular lens - closest
                to the eye
               Objective lens -
                closest to the
                specimen
               Both magnify
               40x objective & 10x
                ocular = 400x
                magnification
Electron Microscopes
 Can magnify 200,000x
 Both electron beam and specimen must
  be placed in a vacuum chamber
 Living cells cannot be viewed
 3 Types
   Scanning Electron Microscopes (SEM)
   Transmission Electron Microscopes (TEM)
   Scanning Tunneling microscopes
Scanning Electron
Microscope
              Specimen is coated
               with a thin layer of
               metal
              3-D image of cell
               surfaces
              Black & white image
               that can be artificially
               colored
Thin metal coating
SEM of Human Blood
Foot of a House Fly
SEM x300
Transmission Electron
Microscope
               Cross section of
                specimen
               Non living
               Stain with metal ions
               Electrons pass
                through specimen &
                form image
               Image is in black &
                white (Can be
                enhanced with color)
Corona Virus (TEM)
Cytoplasm of Liver Cell
(TEM)
Bacteriophages (TEM)
Golgi Apparatus (TEM)
Scanning Tunneling
Microscope
              3D image of the
               specimen’s surface
              Can be used on living
               organisms
Scanning Tunneling Image

				
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posted:3/28/2012
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