Experiment No: 1

Study of Compound Microscope

Objective: To study the various parts and draw the compound
microscope
Requirement: Compound microscope
Principle
The compound microscope has a combination of lenses that enhances both
magnifying power as well as the resolving power. The specimen or object,
to be examined is usually mounted on a transparent glass slide and
positioned on the specimen stage between the condenser lens and objective
lens.
A beam of visible light from the base is focused by a condenser lens
onto the specimen. The objective lens picks up the light transmitted by the
specimen and create a magnified image of the specimen called primary
image inside the body tube. This image is again magnified by the ocular
lens or eye piece.
The compound microscope is called so because, in contrast to a single
magnifying convex lens, it has two such lenses-the objective and the
eyepiece. It magnifies the image of an object that is not visible to the naked
eye to an extent where it can be seen clearly.
Procedure
EYEPEICE

Eyepiece BOOY TUBE

Body tube ROUGH

ADJUSTMENT

Rough adjustment FINE

ARM ADJUSTMENT
Nose piece
High power objective OBJECTIVE LENS
Low power objective
Arm Clip
STAGE
Stoge
Fine adjustmennt Condenser PILLAR IRIS DIAPHRAGM
Iris diaphregm
MIRROR
Mirror

BASE

COMPOUND MISCROSCOPE

1
 Practical Manual
2 Human Anatomy and Physiology - A
follows:
Study the following parts of compound microscope as
A. The support system
B. The focusing system
C. The optical system (magnification system)
D. The illumination system

A. The Support system

horseshoe-shaped base or foot, which
1. Base: It is a heavy-metallic, U-or provide maximum
supports the microscope on the working table to
stability.
from the base and are attached to
2. Pillars: Two upright pillars project upallows
the C-shaped handle. The hinge joint the microscope to be tilted
at a suitable angle for comfortable viewing.
projects up from the
3. Handle (arm or limb): The curved handle, which
hinge joint supports the focusing and magnifying system.
vertically or at
4. Body tube: fitted at the upper end of the handle, either passes to the
an angle, the body tube is the part through which light
eyepiece. It can be raised or lowered by the focusing system.
aperture in its
5. The stage: It is arectangular/square flat platform with an The slide is
center, and fitted to the arm below the objective lenses.
The light
placed on it and centered over the aperture for viewing.
into
emerging from the condenser passes through the slide and objective
the body tube.
B. The Focusing system
screw-heads: It is
It consists of two coarse and two fine adjustment
reference to the
employed for raising or lowering the optical system with
slide tillit comes to the focus. Thus, the adjustments place an objective lens
at its optimal working distance. The coarse adjustment moves the optical
system up down rapidly through a large distance. The fine adjustment is
employed for precise focusing.
C. The Optical (Magnifying) system
1. The body tube: It is a hollow tubular part present between the upper
ends of the objectives and eyepiece. The body tube can be moved up
and down with the help of adjustment screws. The distance between
the upper focal point of the eyepiece and the lower focal point of the
objective is called the optical tube length, which is about 25cm.
 Experiment No: 1 3

it an image
2. Eyepiece: It fits into the top of the body tube and through 5x, 8x, and
replaceable
is seen. Most microscopes are provided withavailable. Each eyeniece
10x eyepieces, though 6x and 15x are also
has two lenses- one mounted at the top, the eye lens and t 3/9
col.
the field lens, is fitted at the bottom. The field lens
divergent rays of the primary image and passes these to the eye
lens,
which further magnifies the image.
fitted at the lower
3. The nosepiece: It is a circular metallic structure
end of the body tube and has fixed and revolving nosepiece. The
Its
revolving nosepiece carries interchangeable objective lenses.
correct position being indicated by a click sound.
its
4. Objective lenses: The magnifying power of each lens and are
numerical aperture (NA) provided rather than its focal length
written on each lens.
a) Low-power objective (10x: NA= 0.25): This lens magnifies the
image 10 times. It is used for initial focusing and viewing a large
area of the specimen slide.
b) High-power objective (45x: NA=0.65): This lens magnifies the
image 45 times. Because of higher magnification, it is used for
more detailed study of the material.
c) Oil-immersion objective (100x: NA=1.30): This lens magnifies
the image 100 times. Since the lens almost touches the slide it has
to be immersed in a special medium (cedar wood oil), a drop of
which is first placed on the slide. The oil is used to increase the
NAand thus the resolving power of the objective. As this lens
gives a total magnification of 1000 times, it is employed for
detailed study of blood cells and tissues.
D. The illumination system
1. Source of light: The source of light may be the diffuse, natural day
light (sunlight) reflected and scattered by the atmosphere and its dust
particles and reflected from the buildings. On bright, sunny days, the
day light is the ideal for routine student work.
If day light is not available, or is not sufficient, an artificial source of
light a fluorescent tube fitted on the working table can provide
enough light.
2. The mirror: A double sided mirror, in fact two mirrors, one flat or
plane and the other concave, fitted back to back in a metal frame is
located below the condenser. It can be rotated in any direction. The
4 Human Anatomy and Physiology -A Practical Manual

plane mirror is used with a distant natural source of light. The

concave mirror is used when the light source is near the microscope.
3. The condenser: It is a system oflenses fitted in a short cylinder that
is mounted below the stage. It can be raised or lowered by a rack and
pinion, and focusing the light rays into a solid core of light on to the
material under study. It also helps in resolving the image.
a) The lens system: It is composed of two lenses. Since the condenser
is a lens system, it has a fixed NA, which should be equal or less than
that of the objective being used. With axes of the two being the same,
all the light passing through the condenser is collected by the
objective, thus allowing maximum clarity.
b) The iris diaphragm: It is fitted within the condenser to adjus. 4/9
of the aperture ofthe diaphragm and regulate the intensity of the iugnt
falling on the material under study.

Observation: Observe and draw a neat labelled diagram of compound

microscope and measure the length of body tube, number of objectives,
magnification of eyepiece, and type of stage.

Precautions
1. Always keep compound microscope in an upright position.
2. Avoid touching lenses with your hands.
3. Keep the microscope covered or in box, when not in
use.

Result: Compound microscope studied in detail and

drawn. A table of observation is made and its diagram has been
values are recorded.