Transcript Mosquito Head SEM x 200 - Independent School District 196

Chapter 3
Section 1 Microscopes
Units of Measure
 Metric system of measurement
 International System of Measurement SI
 Base Unit is the Meter (m)
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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