1. Microscopic Size The Spectrum of Microorganisms

2. Cell Size ► The smallest objects visible to the unaided eye are about 0.1 mm long  Amoeba  Human egg  Paramecium

3. Centimeter ► cm = centimeter ► 1 cm = 1/100 meter ► About the width of your pinky finger

4. Millimeter ► mm = millimeter ► 1 mm = 1/1000 meter ► About the width of a dime

5. Micrometer ► μm = micrometer ► Known as a “micron” ► 1 μm = 1/1,000,000 meter 40-50 microns 6-10 microns Red blood cell Human hair

6. Nanometer ► nm = nanometer ► 1 nm = 1/1,000,000,000 meter 30-50 nm 2.5 nm

7. “Micro”organisms ► In order for an organism to be a “microorganism”, a microscope must be used to see the details of its structure

8. Magnifications ► low-power magnification:  4x (objective lens) x 10x (ocular lens) = 40x ► medium-power magnification:  10x (objective lens) x 10x (ocular lens) = 100x ► high-power magnification:  40x (objective lens) x 10x (ocular lens) = 400x

9. Low-Power (40x) Field of View Diameter Field of View Diameter = 5 mm μm How many μm is this? μm μm There are 1,000 μm in 1 mm, so 5 mm x 1,000 = 5,000 μm

10. Medium-Power (100x) Field of View Diameter

11. High-Power (400x) Field of View Diameter