Microscope Laboratory Activities 2023
Microscope Laboratory Activities 2023
Microscope Laboratory Activities 2023
Generally, cells of plants and animals are too small to be seen with the naked eye, thus, necessitating the
use of special instrument. Such instrument is a microscope, which may be of two general types: a) the light
microscope which makes use of visible light; b) the electron microscope, which makes use of a beam of electrons
rather than visible light.
The compound microscope is an example of a light microscope that makes use of two sets of lenses:
a) a primary magnifiers, the objectives, the lenses of which are immediately next to the specimen being studied;
and b) the secondary magnifiers, the ocular or eyepiece, the lenses of which are immediately next to the eye.
Important terms in microscopy:
1. Virtual image or floating image – image seen in the microscope field.
2. Microscope field – circular area seen through the ocular where the image of the specimen is observed.
3. Magnification – ratio of the apparent size of the object, as seen through the microscope, and the actual size of
the object.
a. total magnification or total power – product of the magnifying capacity of the eyepiece and the
objective being used.
Ex. high power objective 40x
Ocular 10x
Total power 40 x 10 = 400
This means that the image is 400 times as big as the object under study.
4. Units of measurement
a. micrometer (m) – unit of measurement of a light microscope which is equivalent to 10-6.
b. nanometer (m) – unit of measure of an electron microscope that is equivalent to 10-9.
5. Focusing – the adjustment of the spatial relationship between the objective lens and the specimen. When a
clear image of the specimen is seen through the ocular lens, the specimen is said to be “in focus”.
6. Focal length of focus – the distance from the optical center of the lens to the focal point.
7. Working distance – the distance between the front (bottom lens) of the objective lens system and the top of
the cover glass.
Note: Lenses of high magnification and short focal lengths have a short working distance.
8. Angular aperture – the angle or cone of light rays, capable of entering the front lens of the objectives from the
point in the object.
Note: More light rays from the specimen can be taken in by the lens if the angular aperture of the
objective is increased, thus increasing also the resolving power.
9. Numerical Aperture (NA) of an objective – the measurement of the angle of the maximum cone of light that
may enter the lens, or simply a measurement of the ability of the condenser and objective lens to gather light.
Objective Numerical Aperture
4x 0.10
10x 0.25
20x 0.40
40x 0.65
Note: The higher magnification of the objective, the larger is the numerical aperture (NA).
10. Resolving power (RA) – the ability of the lens to clearly separate or distinguish two points or two lines
individually in the image.
11. Depth of focus – represents the thickness of the specimen that may be seen in focus at one time.
- decreases with an increase in the numerical aperture and magnification.
12. Parfocal – term applied to the objective lens when practically no change in focus has to when one power is
substituted for another.
Note: Only a slight turn of the fine adjustment is needed when a change is made from low power to a high
power objective.
13. Refraction – bending of light away from the objective lens when light passes from the glass of the microscope
slide to the air.
Note: Refraction is lessened by using oil (oil immersion objective).
14. Cover glass – thin glass (0.17 to 0.18 mm thick) cut in circles, rectangles or squares for covering the specimen.
I. MECHANICAL PARTS:
1. Base – horshoe or V-shaped structure which supports the entire microscope.
2. Pillar – vertical post extending from the base to the arm.
3. Arm – curved basic frame of the microscope to which the base, body and stage are attached.
- serve as the handle for carrying the microscope as well as providing support for the body tube.
4. Inclination joint – a movable hinge that facilitates tilting of the microscope by holding the arm with your right
hand and the bases with your left hand.
5. Body tube – a hollow cylinder in front of the upper part of the arm and the serves as the optical housing for
the lenses.
6. Draw tube – the smaller cylinder attached to the upper part of the body tube and serves to hold the ocular
eyepiece.
7. Revolving nosepiece – a rotating head attached to the bases of the body tube.
8. Dust shield – a fixed head attached to the base of the body tube.
9. Stage – a platform, which may be circular or square , where the slide with the specimen is placed.
- usually equipped with a pair of clips that hold the slide in place.
- Some microscopes are provided with a mechanical stage adjustment knobs for accurate
movement of the slide.
- Provided with central opening which allows light to pass from the mirror to the object being
studied.
10. Substage condenser with iris diaphragm – a structure found below the stage holding the abbe condenser
above and the iris diaphragm below. The iris diaphragm is provided with a projecting handle or lever which
when manipulated can regulate the amount of light passing through the lenses into the observer’s eye.
11. Adjustment knobs – consist of two pairs of knobs:
a. an upper pair, the coarse adjustment knob or screw which is used for initial focusing by raising or
lowering the body tube with the scanner or the low power objective in position.
b. A lower small pair, the fine adjustment knob or screw which is used for final viewing and adjustment
at different depths, with the high power objective in position.
Note: Never use the coarse adjustment screw when focusing with the high power objective or any high
powered objective. Use only the fine adjustment screw. The coarse adjustment screw can be used when
the low power or scanner objective is in place.
1. Mirror – usually two-faced, of which one surface is plane or flat while the other side is concave (parabolic)
- held by a double-hinged mirror rack or fork which facilitates adjustments at any desired
angle since the mirror functions to reflect the light into the specimen.
- The concave mirror is used with low intensity light which may be either natural or
artificial, while when the source of light is very bright, the plane mirror is best used.
2. Condenser (abbe condenser) – the substage optical element which may be fixed or provided with adjustment
for lowering or raising.
- functions to condense and concentrate reflected light from the mirror through the
specimen at a precise angle to illuminate the microscopic field.
Microscopes are expensive tools, hence, must be handled very carefully at all times. The following are
some of the precautions that you must be familiar with when using them.
a. Examine your microscope before using it for any defects, like misplaced or missing parts. If there is
anything wrong with it, call the attention of the instructor, otherwise you will be held responsible for
any defects.
b. Keep it clean before and after using with a piece of soft cloth (not your handkerchief).
c. Do not separate loose parts, like the ocular or objectives, as they may collect dust.
d. Do not touch the lenses with your fingers. Use lens paper only to clean them.
e. Always check the parts thoroughly after receiving it from the counter and before returning.
f. If anything is spilled on the microscope, clean it off immediately.
g. Always carry the microscope carefully with one hand under the base and the other hand around the
arm. Never carry the microscope hanging like a basket with only one hand.
Name/s: ______________________________ Date Performed: __________________
Group No. _____________________________ Date Submitted: ___________________
This exercise affords the opportunity to become familiar with the essential principles of microscope use.
Through practice, your technique with the microscope improves.
I. Position:
a. Place the microscope on the table with the arms toward you and the base at a safe distance from the
edge of the table so that you do not cramp your body when you look through the eyepiece.
b. Swing the low power objective in position directly above the stage aperture.
II. Lighting:
a. Open the diaphragm wide. Make sure that the top lens of the condenser is at the same level with the
stage.
b. Look through the ocular and adjust the mirror until you get the greatest possible amount of light
reflected in the objective. If the field of the microscope is properly lighted, you should see a circular
area of light that is uniformly bright.
III. Locating the object under the lower objective:
a. Cut out a letter “e” from the classified ad of a newspaper. Place this letter in an upright position on a
clean slide with a drop of water and cover with a cover slip.
b. Look at the objective from the side and turn the coarse adjustment knob until the tip of the objective
is about 2 mm from the cover glass. Remember not to let the objective touch the cover slip for it may
damage or break the lens of the objective or the cover slip.
c. With both eyes open, look through with one eye and slowly turn the coarse adjustment knob until the
image of the object comes into clear focus.
d. Center the object by moving the slide in the right direction and clip the other end of the slide in
place. Change the opening of the diaphragm until the field is just bright enough for you to see the
details of the object clearly. Too strong a light is hard on your eyes.
e. Look at the upright letter through the microscope under low power.
f. Bring the image to a sharper focus by turning either direction the fine adjustment knob.
g. Look at the upright letter “e” through the microscope.
Answer the following questions:
1. Is the letter right side up or upside down? Explain.
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2. Reverse the position of the slide. Is the letter right side-up now?
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3. Now move the letter from the right to left on the stage. Which way does the letter seem to move
as you see it in the ocular? Why is it so?
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h. Once you have learned how to use the low power objective, you should have no difficulty in using the
microscope with the high power objective. The microscopes assigned to you have objectives adjusted
by the maker so that they are parfocal. This means that when an object can be clearly seen under low
power, the objective can be shifted to the next higher magnification with little or no change in focus.
Note: 1. When starting with a microscope study, always examine the specimen under the LPO
first before shifting to HPO.
V. Magnifying Power
The compound light microscope is used to examine details of cellular and tissue structure of animals. The
usefulness of a light microscope is limited not by its ability to magnify objects, but by its ability to discern small
objects that are very close together. This is called RESOLUTION and is related to the wavelength of visible light
used to illuminate an object.
The microscope allows the biologists to extend the vision to a resolution of fractions of a micrometer. This
degree of resolution requires sophisticated electron microscopes, not generally used by undergraduate students.
Lower magnification, however, are just as useful for most aspects of animal biology. For undergraduate laboratory
work, microscopes of magnifications ranging from 5x to 1,000x is commonly used.
a. To find the total magnifying power of the microscope, multiply the magnification of the objective by
that of the ocular. The magnifying powers are marked on both parts. Compute the magnifying power
of the microscope assigned to you, using both the low power and the high power objective.
b. Magnifying power is in terms of diameters, not in areas. A 10-X lens makes a line appear to be ten
times longer than without magnification.
c. In microscopic work, a common unit of measurement is the micron (µ). A micron is 1/1000 of a
millimeter (1 millimeter = 1,000 µ).
Links that will help you on the microscope activities, since you cannot perform actual manipulation of
microscopes.
The microscope is an essential tool in the study of the fine structure of animals. It enables you to see the
animal structures too small to be seen with the naked eye. The microscope is made up of a system of lenses that
can invert images. It is important to learn the correct use of this tool from the start so that you realize its full
potentialities. The accuracy and value of many of your observations in the laboratory will depend on your skill in
the use of this instrument.
2. What are the illuminating parts? Describe and discuss them in your own words.
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3. What are the magnifying parts? Describe and discuss them in your own words.
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4. What are the mechanical parts? Describe and discuss them in your own words.
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5. How important is the use of microscope and the technique’s application in your subject in anatomy and
physiology as well as a BSED Science student?
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Group Activity
Next week (Face to face or Virtual)
MICROSCOPY
GROUP TASKS