1. MICROSCOPES

2. MOST IMPORTANT TOOL OF THE LABORATORY FOR STUDYING MICROORGANISMS

3. TERMS

4. Magnification – ability to enlarge objects
Resolution – ability to show detail
Contrast—the number of visible shades in a specimen

5. PRINCIPLES OF LIGHT MICROSCOPY
Magnification
Microscope has two magnifying lenses
Called compound microscope
Lens include
Ocular lens and objective lens
Most bright field scopes have four magnifications of objective lenses, 4x, 10x, 40x and 100x
Lenses combine to enlarge objects
Magnification is equal to the factor of the ocular x the objective
10x X 100x = 1,000x

6. EFFECT OF MAGNIFICATION

7. PRINCIPLES OF LIGHT MICROSCOPY
Resolution
Resolving power determines how much detail can be seen
Resolution is enhanced with lenses of higher magnification (100x

8. TYPES OF MICROSCOPES

9. COMPOUND LIGHT MICROSCOPE
Light Microscopy
Light passes through specimen, then through series of magnifying lenses
Most common and easiest to use is the compound light microscope

10. COMPOUND LIGHT MICROSCOPE

11. PATHWAY OF LIGHT

12. Principles of Electron Microscopes
Uses electromagnetic lenses, electrons and fluorescent screen to produce image
Resolution increased 1,000 fold over compound light microscope
Magnification increased to 100,000x
Two types of electron microscopes
Transmission
Scanning

14. Types of Electron Microscopes
Transmission Electron Microscope (TEM)
Used to observe fine detail
Directs beam of electrons at specimen
Electrons pass through or scatter at surface
Shows dark and light areas
Darker areas more dense
Specimen preparation through
Thin sectioning
Freeze fracturing or freeze etching

15. Types of Electron Microscopes
Scanning Electron Microscope (SEM)
Used to observe surface detail
Beam of electrons scan surface of specimen
Specimen coated with metal
Usually gold
Electrons are released and reflected into viewing chamber
Some atomic microscopes capable of seeing single atoms