MICROSCOPE
Lab Exercise # 1
Objective: Structure, function and operation of the Light
Microscope.
I. Introduction:
The microscope (micron = small, scope = application) is an instrument that is
generally used to study the very small organisms (microorganisms) or particles
which are not visible by the naked eyes. Anton Van Leeuwenhoeck (1674) made
the microscope for the first time. This microscope has practically been made with
the combination of two lenses so it is also termed as Compound Microscope.
Eventually, it also has a provision of using the source of light thus sometimes it is
also named as Light Microscope. However, both names, Compound Microscope
and Light Microscope are justified and correctly used for the same instruments.
The naked human eyes have an ability to see smallest object of 0.1 mm, only whilst
the invention of this Microscope made it possible to see much smaller object i .e ....
0.2um or 200nm. This characteristic of seeing the minimum distance of 200nm
between the two particles is called Resolution Power. The microscope enlarges the
view image of an object up to 1000 times of its original size and the times of
enlargement is called as Magnification Power. The microscope is an expensive
instrument so it requires great care in handling it.
11. Materials and Methods:
Basically, variety of microscopes are available today and these are able to
magnify the image ranging from 5 times by Simple Microscope to 2,00,000 times
by Electron Microscope. Microscopes are classified as follows:
Microscopes
------------------------~----------------~-Simple Microscope
Compound Microscope
(two sets of working lenses with exlra
(a single lens also known as
provision of source of light)
Electron Microscope
(Electron beam is used in place of
lenses to magnify the image)
magnifying lens)
Monocular 1 Binocular (with
r
Light Microscope
\
Phase Contrast Microscope
I
Camera Microscope
Inverted licroscope Fluorescent licroscope
During the study of use and care of the microscope, it is also very important to
know about the different parts of the most commonly used microscope i.e .. Light
Microscope. Only three major portions contribute to make a microscope and these
are 1. optical tube (body tube or lens tube), comprising of Ocular or Eye Piece at its
proximal end and Objective at its distal end. 2. Source of light, which is formed of a
lamp fixed in a socket located on the base or the foot of the microscope. 3. Stage is
the platform to place the slide over an hole to allow the light to pass through the
objects of study. Generally the stage is moveable up and down; right and left and
also forward and backward. The knobs that controls the up and down movements of
the stage are called as adjustment knobs. The knob that makes it move faster is
larger in size and is called as Course Adjustment and the knob that makes it move
slowly is called as Fine Adjustment. For keeping all these parts operating , a solid
body is provided to support these three very important parts.
The magnification of the Microscope is the product of the Power of Eye Piece
and the Power of Objective.
Magnification = Power of the Eye piece X Power of the Objective
U sing Light Microscope is very simple with suggested and right steps which
are listed below:
1. Place the slide on the stage in a position that object falls exactly below the
objective.
2. Fix the lowest powered objective in the beginning and use the course adjustment
to focus it.
3. Then use the objective of higher magnification and use fine adjustment to focus it.
4. For shift or transport of microscope from one place to another always hold the
microscope at its curve or handle or at the base with both hands.
5.To make practical use of the microscope, study letter E under your microscope in
different magnification and observe the difference of size and also draw these
changes.
6. For more practice, prepare a slide of Epithelial Cells of Onion and stain it with
Lugol s Iodine and another slide of Human Cheek Cells (Simple Squamous
Epithelium) and stain it with Methylene Blue and observe these cells under different
magnification and draw and compare those with the skeches below.
Simple Columnar Epithelium
Simple Squamous Epithelium
(Onion Cells)
(Human Cheek Cells)
Plant Cells
Animal Cells
Ill. Observations:
After completing this exercise it is possible 'to answer the following questions.
1. What is a Microscope.
It is an instrument to show minute or small objects .
....
2. What is Resolution Power.
Ability to show minimum distance between two particles or minimum visible size. 3.
What is the Magnification Power and how do you calculate it.
Ability to enlarge the size of the image represented in number of times of
enlargements.
4. What are the most important parts of the Microscope.
1- Optic tube, 2- Source of light, 3- Body of the microscope.
5. Why is it correct to call it '-Light or Compound Microscope.
It needs light to work so it is a light microscope and eye pieces and objectives are the two
sets of lenses make it call a compound microscope
Objective
Optic tube
Stage
Coarse
adjustment
Fine
adjustment
Condenser