1. COMPOUND MICROSCOPES ( LAB
COMPOUND MICROSCOPES ( LAB. TUTORIAL FOR FIRST YEAR STUDENTS OF DENTISTRY)
Dr. Ammar Jusmani/ m.b.b.s /MSc. Clinical Microbiology /
Ibn Sina University of the Medical & Pharmaceutical Sciences

2. MICROSCOPY BASICS:OBJECTIVES
1) Learn proper use & care of compound microscope.
2) Learn how to view specimens at different levels of magnification.
3)practice universal precautions.
4)Learn how to make a wet mount slide of a specimen.
5)Learn how to obtain and label photomicrographs of specimens.
6)Use the terminology (listed) correctly.

3. DEFINITIONS
DEPTH-OF-FIELD: This is the vertical distance that is in focus at any one time.
The higher the magnification the smaller the depth-of-field, meaning only a thin horizontal slice of your sample is seen in focus.
PARFOCAL: This feature refers to the ability to change from one objective lens to another and still have the specimen in focus without having to focus more than a little; so you can switch from low power(scanning) to high power with ease.

4. Microscopy Terminology
Students should use & define the following terms:
1) Compound microscope 2) Depth of field
3) High-dry power ) Iris diaphragm
5) Low power ) Nose piece
7)Objective ) Oil Immersion
9)Ocular ) Parfocal
11) Resolution ) Scanning power
13) Total Magnification 14) Universal precautions
15) Wet Mount ) Bacterial smear

5. COMPOUND MICROSCOPES 1) Attend to MICROSCOPE STATION
2)Remove cover, fold it neatly and place it where it won’t interrupt your work.
3)Leave microscope at where it is resting.
4)Raise by holding from NECK and SUPPORT at BASE.
5) Switch on from base.
6)Control light: Too much light washes out the field being examined; too little light reduces illumination, hence field will not be clear.
7)Adjust light: this is done with a DIAL at the base from the other side of the main switch.
8) IRIS DIAPHRAGM: Another way to ADUST LIGHT: this mechanism is like a camera lens; twist it to open and close the stage.

6. COMPOUND MICROSCOPE
9) Mechanical stage: this is where you place your specimen slide into the slide(GRIP) holder, and then adjust the position of the slide using the KNOBS at the side of the stage: this way you can send in your specimen very easily.
10) Focus knobs: Raise and lower your specimen in a vertical position. This determines whether your specimen is in focus or not: there are two knobs: -COARSE FOCUS KNOB: this is closest to the body of the microscope.
-FINE FOCUS KNOB: farthest from the body of the microscope. Fine focus clears the image from blurring.

7. COMPOUND MICROSCOPE
11) Ocular lens: Single or Binocular: TheLeica (DM-750) is a M
It has a viewing tube that consists of Integrated Eye pieces that are preset with thumb screws and therefore do not need to adjust or install the eyepieces.
The ocular lens magnifies the specimen (10x) the actual size.
12) Objective lens: These are located and Rotated at the NOSE PIECE- they are turned and rotated into the right position to bring the image into focus.
The shortest objective lens is the one with the RED BAND around it: It is called the (LOW) FOCUS POWER/ It magnifies the specimen (4x) its actual size: so with the power of the Ocular lens, Which is (10x), The TOTAL MAGNIFICATION POWER IS (10x) x(4x) = 40x the actual size of the specimen that is being examined.

8. COMPOUND MICROSCOPE
13)Next Low Power lens: This objective lens has a YELLOW BAND around its lower end. It magnifies the specimen (10x) its actual size, so the TOTAL MAGNIFICATION POWER IS
(10x) X( 10x) = 100x the actual size of the specimen.
14) Objective lens with a power of (20x): Calculate the Total Magnification Power with this lens.
What is the colour of this ojective lens?
15)High Dry Power: This is of Intermediate Length. It has a BLUE STRIPE around it. It has a Power of (40x). Calculate the total magnification power.
N.B. This objective lens is usually covered with a rubber glove to protect it from oil, which may destroy it.

9. COMPOUND MICROSCOPE
16) Oil Immersion lens : This is the longest objective lens and it has a black band around it. It is used when viewing bacteria.

10. STORING THE MICROSCOPE
1) Microscope stage should be clean
2) Oil should e cleaned from the oil immersion lens and all other parts.
3)(4x) objective lens should be clicked back into space.
5) Stage should be in the lowest possible position.
6) Dust cover should be on.

11. DEFINITIONS IN COMPOUND MICROSCOPES
RESOLUTION: This term is derived from the resolving power of the lens. It is the smallest distance at which two points can be seen separately.
The resolving power of the human eye at (10) inches is (o.1)mm.
This resolution increases if you use the microscope to aid your eye and further increases as you use higher levels of magnification.
There is a limit to this resolution, therefore more powerful microscopes are used such as the electron microscope.
Electron microscopes are used to resolve smaller structures like the delicate structures such as bacterial flagellae and the more tiny structures in viruses.

12. DEFINITIONS
REFRACTION: This phenomenon refers to bending of light to one side or the other as it emanates from the light source. Refracted light is lost and it becomes harder for you to see your sample or object.
Refraction can be overcome if you place a drop of oil between the sample slide that is on the mechanical stage and the glass lens of the objective lens.
Oil Immersion is considered to be a modern microscopy technique.

13. DEFINITIONS
DEPTH-OF-FIELD: This is the vertical distance that is in focus at any one time.
The higher the magnification the smaller the depth-of-field, meaning only a thin horizontal slice of your sample is seen in focus.
PARFOCAL: This feature refers to the ability to change from one objective lens to another and still have the specimen in focus without having to focus more than a little; so you can switch from low power(scanning) to high power with ease.

14. DEFINITIONS
WORKING DISTANCE OF THE LENS: The distance between the lens and the slide when the specimen is seen in sharp focus.
The higher the magnification the smaller the working distance.
N.B. To avoid ramming a long objective lens into a slide observe the working distance rule: Use the coarse adjustment knob on LOW POWER objective lens.

15. MICROSCOPIC EXAMINATION OF CELLS
PLANT CELLS:
MATERIALS NEEDED:
1) microscope
2) biohazard bags
3) dropper bottle of D/W, physiological saline, Iodine, Methylene blue.
4) Onion bulb.
5) disinfectant tray.
Procedure: Wrap a thin epidermal layer of onion skin around a sample slide and spread it out neatly on the slide.
Mount your specimen by placing a drop of methylene blue or iodine on it.
Now cover the specimen with a cover slip.

16. PLANT CELLS, CONTD… YOUR SPECIMEN IS NOW READY FOR EXAMINATION.
With your Leica (DM-750) view your sample using the different levels of magnification available on your microscope.
-Draw what you see
-Document the power of the objective and ocular lens
-Work out the total magnification power at each level of examination.

17. ANIMAL CELLS MATERIALS NEEDED: 1)microscope (DM-750) 2)Tooth picks
3) methylene blue stain
4) disinfectant tray
5) biohazard bags
6) dropper
Procedure:
Obtain cell scrapings with toothpick from inside of cheek.
Rub your toothpick in a drop of saline on a microscope slide AND Make a WET MOUNT by applying a drop of methylene blue stain then add a cover slip.
AT the end of examination make sure you have properly disposed of any hazardous material.
Store your microscope properly.