1. Safety & Microscopy

2. Safety Rules
1. Wear a laboratory apron or coat when- ever you are working with chemicals or heated substances.
2. Do not wear sandals or open-toed shoes in the laboratory. Never walk around the laboratory bare- foot or in stocking feet.
4. Be serious and alert when working in the laboratory. Never “horse around” in the laboratory.
5. Never perform activities that are not authorized by your teacher.

3. Safety Rules
6. Never eat or taste anything. This includes food, drinks, candy, and gum.
7. Wash your hands before leaving the lab.
8. Know the location and proper use of safety equipment such as the fire extinguisher, fire blanket, first-aid kit, safety shower.
9. Keep your laboratory area clean and free of unnecessary books, papers, and equipment.

4. Some types of microscopes
Brightfield microscope
Darkground microscope
Phase contrast microscope
Fluorescent microscope
Electron microscope

5. Microscopy
Microorganisms : cannot be seen by naked eye.

6. Microscopy Human eye resolving power : ~ 200 um (micrometers)
*Sizes of Microorganism.
Bacteria : ~ 0.5–5.0 um
Fungi : > 2 um
Parasites : > 5 µm
Viruses : < 0.30 um
Light microscopy: Bacteria , fungi & Parasites.
- ~0.2 um
Electron microscopy : Viruses
- ~0.002 um ( 2 nm)

8. Condenser Lens: The function of the condenser lens is to collect the light from the illuminator and focus it on the specimen.
Diaphragm or Iris: The diaphragm is used to control the amount of light reaching the specimen. In a student scope it is a rotating disk under the stage and above the condenser.
Rules for Using the Microscope
1. Use two hands to carry a microscope, one hand holding the arm, the other
holding the base.
2. Only use lens paper and water to clean the lenses.

9. Magnification : the ability to make small objects seem larger
microscope has 4 magnifications: Scanning, Low , High & oil immersion. Each objective will have written the magnification. In addition to this, the ocular lens (eyepiece) has a magnification. The total magnification is the ocular x objective.
Resolution: the ability to see fine details.
Contrast: the ratio between the dark and the light. (difference in color)
Magnification
Ocular lens
Total Magnification
Scanning 4x
10x
40x
Low Power
100x
High Power
400x
Oil immersion
1000x

10. Focusing Specimens *Field of View:
Always start with the scanning objective.
Once you've focused on Scanning, switch to Low Power.
Now switch to High Power.
*Field of View:
The field of view (FOV) is the actual “circle” you see when looking in the microscope.

11. Numerical Aperture NA
NA means The light-gathering ability of a microscope objective.
The higher the NA value the better the resolution.
For 100x lens , we usually add oil between the lens and slide. why ?
- This is because that the refractive index of air is 1 and oil is ~ 1.5.
So, NA value increases with oil.