A microscope is the most
important instrument use to view the things that cannot be seen with the naked
The microscope was available
during the mid 1600s. In 1665 an English scientist named ROBERT HOOK develop optical microscope and made key observation .He
observed the cells using the optical microscope.
ANTON VAN LEEUWEN-HOEK ( 1632-1723) discover simple glass lens of
convex surface and made successful observation of microscopic organisms which
he named animalcules. He is consider as one of the first who give the correct
description of protozoa , fungi and bacteria.
In 1870 ERNT ABBE develop a compound microscope
lens that help to create magnified and fine images. He also develop oil
immersion lens for improve resolution as well as clarity of image.
Ø TYPES OF
There are two types of
1. Light microscope
2. Electron microscopeü LIGHT
MICROSCOPEThe light microscope which
is used in laboratory is called compound microscope in which visible light or
uv lights are used to illuminate the objects.Light microscope consist
of four system.a. The support systemb. The magnification systemc. The illumination systemd. The adjustment systema.
THE SUPPORTIN SYSTEM :It include main body
components.Foot: The bottom of
the microscope used for support.Resolving nosepiece: It holds two or more objective lenses and can
allow rotation to easily change the power.Stage: The flat platform used to place the slide.Stage clip: It holds the slide in proper place.Arm: It is the tube connected to base of the microscope.b. THE
MAGNIFICATION SYSTEM :It is fixed at the bottom
of the body tube just above the preparation under examination. This system
consist of two lenses:1. Objective lens : It has different powerLow power 10x (5 – 6 mm)High power 40x (0.5 – 1.5 mm)Oil immersion 100x (0.15 – 0.20 mm) 2.
Eye piece :It is present on the top of the body tube where you place your eye it is also
called ocular.Numerical aperture: It is the measurement of the angle maximum
cone of light that can enter the objective. Resolving power: the ability of the lens to distinguish with
two objects at a particular distance apart.Working distance: working distance of an objective is the
distance between the front lens of the objective and the object slide when the
slide is flows.Total magnification: Total magnification = magnification
of objective lens x magnification of
THE ILLUMINATION SYSTEM :Source of light: A steady light source used in place of a
mirror.Mirror: two type of mirror concave sight and plane sight , if
microscope has a mirror , it is used to reflect light.Condenser: The purpose of the condenser lens is to focus
the light onto the specimen between the mirror and stage.Diaphragm: It regulates the amount of light on the
ADJUSTMENT SYSTEM : 1. course adjustment system: It is used first to achieved an appropriate
focus.2. Fine adjustment screw: It is used to bring objects into perfect
focus.3. Condenser adjustment screw: It is used to raise or lower the condenser in
order to adjust the illumination.4. Iris diaphragm lever: It can be moved to closed or open the
diaphragm this reducing or increasing the intensity of life.
5. The mechanical stage: These are usually two screw which are use to
move the glass slide on mechanical stage. One of them is used to move a slide
backward and forward while the other moves the slide right and left