Experiment: 1
Title: Study Simple Microscope and B) Compound Microscope.
Aim: To study the structure and function of microscope A) Simple Microscope and B)
Compound Microscope.
Apparatus required: Simple microscope & Compound microscope.
Microscope and its Uses
The instrument, through which very tiny objects can be seen by magnifying the objects, is
known as Microscope (Greek word Micros means tiny +skopeein means see). The inventor of
microscope is Antony Von Leeuwenhoek (actual spelling is Antoj van Leeuwenhoek).
Microscope may be of various types e.g. Optical (light) Microscope. Electron Microscope and
Phase Contrast Microscope etc. We use Light Microscope in our laboratories. Optical
Microscope again is of two types: (a) Simple Microscope and (b) Compound Microscope.
A. Simple Microscope:
The instrument is called Simple Microscope because the structural and functional devices of it
are simple. Comparatively larger organs or it parts are usually observed or dissected with the
help of this microscope. That is why this microscope is called Simple Microscope. The structure
and uses of a Simple Microscope are stated below:
Structure: The structure of a simple microscope is very simple. It has a body, a stage made of
thick glass for placing slides, two clips to fix the slides, a handle, an eyepiece placed with the
handle and a mirror. There is an adjustment knob by which the eye piece may be moved upward
and downward. The entire body stands on the base or foot.
Functioning: In simple microscope, convex lens of short focal length is used to see magnified
image of a small object. The object is placed between the optical centre and the focus of a
convex lens, its image is virtual, erect and magnified and on the same side as the object.
B) Compound microscope
The structure of a compound Microscope is quite complex and its working process is also
complicated. Different parts of a compound microscope and theit functions are described below:
The different parts of a compound microscope again may be divided into two groups: 1)
mechanical and 2) Optical parts
1) Mechanical Parts:
A) Base or foot : The flat part on which the entire body of the microscope is situated is called the
Base or Foot .
B) Pillar: The vertical part placed in the backside of the base is called the pillar.
C) Arm: The upper beend part flexibility fixed with the pillar by a screw is the arm . Holding
the Arm we use to move the microscope.
D) Body tube: it is along tube. It is fixed at the end of the bend arm. There are two screws at the
junction of the arm and the body tube. One of the screw is called Coarse Adjustment and the
other one is called fine adjustment by turning these screws the body tube maybe the body tube
maybe moved upwards or downward as per requirement.
E) Draw tube: The drawtube is inserted inside the body tube. It may be pulled upwardly when
necessary.
F) Nose piece: It is circular body fixed at the lower end of the body tube. It is provided with
three holes with spiral threads in its inner wall where objectives of different magnifications are
attached.
G) Stage: The stage is rectangular and attached with the arm at the base. There is a hole at the
center of the stage through which light is focused. Two clips are fixed on the stage at its base
slide is fixed on the stage with the help of the clips.
H) Diaphragm: By Expansion and contraction of this part as certain the amount of light to fall on
the slide.
I) Coarse and fine adjustments: At the top of the arm there are two large screws on two sides;
these are called coarse adjustments screws. With the help of these screws the draw tube may be
moved upwards or downwards rapidly. Another pair of comparatively small screw is present
below the coarse adjustments screws. The drawtube may be moved very slowly up and down, by
moving these screws. These screws are known as fine adjustment screws.
2. Optical parts: Eye piece: it is a small tube, which can be inserted into the drawtube. There are
two lenses fitted at its two ends. Keeping the eyes on this eyepiece object placed on the stage is
to be observed
Objectives: There are also small tubes like eyepiece and they are
provided with lenses. Usually three objectives of different magnifications
are attached in three holes of the nosepiece. Magnification power is
inscribed on the body of the eyepiece and objectives.
Condenser: it is simple a combination of two lenses. It is attached beneath
the hole of the stage. Light being converged through this condenser fall
on the specimen placed on the slide.
Mirror: it is aplano-concave mirror. It is attached at the base of the pillar.
Light can be focused through condenser and diaphragm, by turning the
mirror at the necessary direction.
The magnification determined by multiplying the power inscribed on the eyepiece
and objectives.
Questions viva voice:
Which type of image do you observe under the compound microscope?
What is the function of condenser?
What is the difference between simple and compound microscope?
