chapter 3

Chapter 3Section 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