Basics only Microscopy is the technical field that uses microscopes to observe samples which are not in the resolution range of the normal-unaided eye.  Microscope is a scientific-instrument consisting of magnifying lens that enables an observer to view the minute features distinctly.  In greek, micro = small skopein = to view.

1. MICROSCOPY 1
MICROSCOPY
 Microscopy is the technical field that uses microscopes to observe samples which are
not in the resolution range of the normal-unaided eye.
 Microscope is a scientific-instrument consisting of magnifying lens that enables an
observer to view the minute features distinctly.
 In greek, micro = small
skopein = to view.
THE HISTORY OF MICROSCOPES
1590 - Zaccharias Janssen and Hans Janssen (Dutch eye glass makers) experimented
With multiple lenses placed in a tube, observed greatly enlarged objects.
1609 - Galileo Galilei developed a compound microscope with a convex and concave lens.
1625 - Giovanni Johannes Faber coined the term microscope.
1660s- Extensive use of microscopes in research (Italy, Holland and England).
1665 - Robert Hooke looked at a silver of cork through microscope lens & noticed “cells”.
1670 -Antonie Van Leeuewenhoek (Father of microscopy) made the single lens
Microscope & developed magnifying lens (~300X).
17th century - Christiaan Huygens, developed a simple 2 lens ocular system
1893- August Kohler developed a key technique for sample illumination.
1903- Richard Zsigmondy developed ultra microscope (Nobel Prize in Chemistry, 1925).
1931 - Ernst Ruska co & Max Knoll invented the electron microscope.
1932- Fritz Zernike invented the phase-contrast microscope that enabled the study of
colourless and transparent biological materials (Nobel Prize in physics, 1953).
1981-Gerd Binnig & Heinrich Rohrer invented Scanning tunnelling microscope (Nobel
Prize, 1986).
USE OF MICROSCOPES IN CYTOLOGY
Life-scientists use the invaluable tool in the field of medicinal diagnosis and research.
 To visualize the crystalline and molecular structures of cells.
 To conduct cytological screening for blood disorders and other diseases
 To study microorganisms, this allows scientists to develop the vaccines. Being able to
identify the infecting agent is the basis for effective treatment.
 To map the fine details of the spatial distribution of macromolecules within cells.
 To measure the biochemical events in the living tissues.
 To interpret the function of proteins within cells by labeling the proteins with a tag.
 To review chromosomal structure particularly in chromosome abnormalities by
staining techniques.
 To Examine Forensic evidence.
 To study the failures in immune function and molecular studies
 To obtain Digital imaging for storing images and in obtaining second opinions or
returning results to remote locations.
 To monitor the health of a particular ecosystem.
 To diagnose and get symptoms details in the veterinary clinic.
NOTE:
The word "lens" comes from the lentil because the shape of a convex lens is similar to that of a
lentil.

2. PRINCIPLE: MAGNIFICATION AND RESOLVING
MAGNIFICATON
 Magnification is defined as “
microscope for detailed analysis of
 The magnification by microscope is the product of individual magnifying powers of
ocular lens (eye piece) and objective lens.
Magnification = Magnifying Power of ocular lens X Magnifying Power of objective Lens
For example:
If ocular lens is 10X and objective is 40X. Then,
Magnification = Magnifying Power of ocular lens
= 10 X 40
= 400X
 The Magnifying Power of Microscope is defined as “The ratio
through the microscope to the size of sample observed via naked eye”.
Magnifying Power = The ratio of the final image observed through the microscope
 Magnification has no limit, but beyond certain point the view becomes blur or
This is termed as EMPTY MAGNIFICATION
 Therefore, magnification alone does not
Thus, Resolution plays a crucial role.
OPTICAL
MICROSCOPE
SIMPLE
MICROSCOPE
COMPOUND
MICROSCOPE
PRINCIPLE: MAGNIFICATION AND RESOLVING
Magnification is defined as “The degree of enlargement of an object provided by the
microscope for detailed analysis of sample”.
The magnification by microscope is the product of individual magnifying powers of
ocular lens (eye piece) and objective lens.
Magnification = Magnifying Power of ocular lens X Magnifying Power of objective Lens
10X and objective is 40X. Then,
Magnification = Magnifying Power of ocular lens X Magnifying Power of objective lens
Power of Microscope is defined as “The ratio of the final image observed
through the microscope to the size of sample observed via naked eye”.
ratio of the final image observed through the microscope
The size of sample observed via naked eye
Magnification has no limit, but beyond certain point the view becomes blur or
EMPTY MAGNIFICATION.
Therefore, magnification alone does not provide quality information of the sample.
Thus, Resolution plays a crucial role.
MICROSCOPE
OPTICAL
MICROSCOPE
COMPOUND
MICROSCOPE
STEREOZOOM
MICROSCOPE
PHASE
CONTRAST
MICROSCOPE
FLUORESCENT
MICROSCOPE
ELECTRON
MICROSCOPE
TRANSMISSION
ELECTRON
MICROSCOPE
SCANNING
ELECTRON
MICROSCOPE
MICROSCOPY 2
PRINCIPLE: MAGNIFICATION AND RESOLVING POWER
he degree of enlargement of an object provided by the
The magnification by microscope is the product of individual magnifying powers of
Magnification = Magnifying Power of ocular lens X Magnifying Power of objective Lens
Magnifying Power of objective lens
of the final image observed
through the microscope to the size of sample observed via naked eye”.
ratio of the final image observed through the microscope
The size of sample observed via naked eye
Magnification has no limit, but beyond certain point the view becomes blur or unclear.
provide quality information of the sample.
ELECTRON
MICROSCOPE
TRANSMISSION
ELECTRON
MICROSCOPE
SCANNING
ELECTRON
MICROSCOPE

3. MICROSCOPY 3
RESOLVING POWER
 Resolving Power is defined as “the performance capacity or ability of the microscope to
distinguish between two very closely associated particles”.
For example;
Human eye has resolving power of 0.25nm.
 Resolving Power of the microscope is the reciprocal of limit of resolution.
 Limit of Resolution is the shortest distance between the two objects when they can be
distinguished as two separate entities.
Limit of Resolution (d) = 0.61 X λ
n Sinθ
Where,λ → wavelength of light
n→ refractive index of the medium between specimen and objective
θ→ half angle formed between the specimen and lens
 As, Resolving Power of the microscope = 1 _
Limit of Resolution
 Therefore, Resolving Power of the microscope = n Sinθ
0.61 Xλ
Where, n → refractive index of the medium between specimen and objective
θ→ half angle formed between the specimen and lens
λ → wavelength of light
 Since, Resolving Power of the microscope ∝ n Sinθ
λ
 Resolving power can be increased by following 3 steps:
1. by increasing Refractive Index;
nimmersion oil = 1.5
nair = 1
2. by increasing Sinθ
3. by decreasing wavelength of light;
λblue light= 400nm
λ red light= 600nm
NOTE:
Numerical Aperture (NA) of the objective is defined as the property of lens that decides
the quantity of light that enters into objective.
Numerical Aperture = n Sinθ