E1: Microscopes and
Magnification
Progress
Rep 1(1D)
Done
⭐⭐⭐(Aug 15)
Rep 4(2W)
Rep 2(3D)
Rep 3(1W)
Week
Prelim
Links
Exercise 1. MICROSCOPES AND
MAGNIFICATION
Microscope
What is a Microscope?
Its a instrument that produces enlarged images of small objects, allowing the
observer an exceedingly close view of minute structures which an unaided eye cant
see.
When is a microscope necessary?
When an object’s is higher than 10 to 12 times of magnification.
A. Compound Microscope
1. Structure
Ten(10) Mechanical Parts of a compound microscope.
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Heavy U- or V-shaped foot on which the microscope stands and makes the
foundation.
Base
A firm support arising from the base. Same as the neck.
Pillar
Platform with central aperture and clips to hold the slide being studied. Where the
specimen is placed and properly secure the glass slides for viewing.
Stage
A stout curved handle used in carrying the instrument. Where to hold aside from
the base for transporting the M.
Arm
The box-like structure attached to the arm and bears the lenses and prism.
Body tube
What part bears the four objective lenses.
Rotating (revolving) nosepiece
A metallic structure above the nosepiece that protects the objectives.
Dust shield
The outer rotary knob that quickly moves objectives to focus or obtain an image of
the object.
Coarse adjustment knob
The inner rotary knob attached within the arm. It is for more delicate focusing
especially at high magnification.
Fine adjustment knob
Found on top of the body tube into which ocular is inserted; can be rotated 360⁰ for
ease of viewing.
Draw tube
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Five(5) Optical Parts of a compound microscope.
Found below the stage; serves to gather and direct the light to illuminate the object.
The concave mirror will gather more light than the flat (plain) mirror, but the latter
provides more satisfactory lighting at high magnifications.
Mirror
A metal plate with different diameters of circular openings that control the amount of
light reaching the object.
Iris diaphragm
Found between the mirror and the stage and serves to further concentrate light rays
on the specimen.
Condenser(lens system)
Objectives of object lens – consist of two or more lenses fixed in a rigid mount
that serve to form a real image of the object within the body tube.
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1. Scanner – smallest and shortest, with lowest magnification but allows viewer to
see a greater area.
2. Low power objective (LPO) – shorter lens with a magnifying power of 10x.
3. High power objective (HPO) – the longer lens that magnifies 40x and forms a
bigger image of the object.
4. Oil immersion objective (OIO) – the longest objective, with a magnifying
power of 100x, used only with immersion oil.
Two larger lenses at the top of the draw tube that serve to further magnify the
image. The lens of the ocular refracts (bends) the light rays passing from the real
image to the retina of the eye in such a way as to produce the effect of a still virtual
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image (ghost image). The latter is imaginary (it cannot be projected on a surface); it
produces on the eye the same effect as if an object and the size of the virtual image
were held at ordinary reading distance.
2. Care and Learning
What are the acceptable way to care for the microscope?
a. Always be treated with the care accorded to delicate equipment
Rotate the ocular to see if its dirty
Soft towel is used to clean the whole apparatus
b. Lift the microscope in the arms and supported in the base
What are the wrong way in handling a microscope?
Never attempt to disassemble the microscope
Lenses should only be cleaned with lens paper
3. Microscope Slide Preparation
What is a Microscopic Object?
It is a very small specimen which we cannot see with the naked eye without any use
of an instrument to aid us.
What makes a Temporary(fresh) Mount?
The object to be examined is then stained to give color to the various parts and
surrounded with a liquid and covered with a slip
What makes a Permanent Mount?
The object to be examined undergoes a long process os killing, washing, staining,
dehydrated in alcohol, and mounted in a Canada balsam.
Animals and tissues are coated in Paraffin wax and are thinly cut to 10 micra (µ) =
0.01 mm in a precision machine(Microtome).
4. Use of a Microscope
Enumerate the steps in using a microscope.
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a. Place the microscope before you in an upright position, and with the arm
towards you.
b. Check the mirror and lenses for cleanliness. Remember, use only lens tissue in
cleaning these lenses.
c. Place the slide to be studied on the stage in such a way that the part to be
observed is centered over the hole in the stage.
d. Place the clips over the ends of the slide in such a manner that the slide will be
held securely in place.
e. Adjust the mirror so that the specimen is evenly illuminated. The flat side of the
mirror is best when using a microscope with a condenser. Turn the mirror so
that the light from above or from the window is reflected up through the object
and into the body tube. Never use direct sunlight.
f. The opening of the diaphragm is very important. Size of the opening should be
selected for every slide and magnification change. Most beginning students use
too much light.
g. When viewing the specimen, never squint. Try to keep both eyes open, this
reduces eyestrain.
h. With the monocular microscope, try to use the left eye. This leaves your right
eye for your drawings, and you will be able to look and draw at the same time.
i. The following are the proper steps in focusing a compound microscope:
Rack down the stage with the coarse judgement.
Place slide over the opening in the stage and position clips.
Turn your head to the side and rotate the nosepiece to bring the lower
objective (shorter) into the optical axis.
Rack the stage all the way up with coarse adjustment while watching from
the side to bring the tip of the objective about one-half inch above the slide.
Look into the ocular lens (eyepiece) and rack slowly upward until the object
is visible. Then use the fine adjustment to clear up the focus.
Now (and only now) the high power objective (40X) may be swung into
position. Watch as you do this to make certain that there is clearance. From
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this point, use only fine adjustment especially if the microscope is parfocal.
B. The Binocular Dissecting Microscope
1. Structure
How does Binocular Dissecting Microscope differ from CM?
Binocular Dissecting Microscopes are for viewing the surface features of a
specimen, whereas compound microscopes are designed to look through a
specimen.
Have depth and dimension
No inverted specimen
What is the function of a Diopter?
is a fine focus adjustment mechanism found right by the eyepiece. It allows you to
adjust the focus for each eyepiece separately
What is Interpupillary Distance means relate to BDS?
the distance between the eyes that is adjusted for the comfort of the viewer
The tube supporting the ocular may be focused separately to compensate for
differences between the eyes of the user.
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2. Focusing and Adjustment
The following with the binocular dissecting microscope in which the left ocular is
individually adjustable:
1. Cover your left eye.
2. Focus the microscope for your right eye on a page of a newspaper.
3. Then, cover your right eye.
4. Focus the left ocular individually until good focus is obtained.
5. Now both oculars will have the same focus for both eyes.
6. Finally, spread the two oculars apart to conform with the distance between your
eyes to be able to view one stereoscopic image.
Magnification
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