compound microscope, phase contrast microscope etc

1. INTRODUCTION TO
MICROSCOPY
Mr.R.R.Patil
Dr.Shivajirao Kadam College of Pharmacy,
Kasabe digraj, Sangli

2. INTRODUCTION
 Defin:
It is an optical instrument consisting of
lens or combination of lenses for
making enlarge or magnified image of
minute object.
The science dealing with all aspects of
a microscope is called microscopy.

3. Classification of microscope
 Depending on number of lenses
i. Single microscope
ii. Compound microscope
 Depending on number of eyepiece
i. Monocular microscope
ii. Binocular microscope
 Depending on source
i. Light or optical microscope
ii. Electron microscope

4. Compound Microscope
In compound microscope three essential
systems included…
 Support system: base, pillar, stage &
body tube.
 Illumination system: light source or
mirror, iris diaphragm & condenser.
 Magnification system: objective &
eyepiece.

5. IMAGE OF COMPOUND MICROSCOPE

6. IMAGE OF BINOCULAR MICROSCOPE

7. IMPORTANT TERMS OF
MICROSCOPY
 Magnification
 Working distance
 Resolving power
 Numerical aperture

8. Magnification
 The degree of enlargement is called
magnification or magnifying power of
the instrument.
 The magnification is effected in two
stages..
i. By the objective lens
ii. By the eye-piece lens

9.  Magnification of the microscope can
be calculated by multiplying the
magnification power of the objective
by that of eye-piece.
 The magnifying ability is denoted by
‘X’ symbol.

10. Working distance
 Defined as the distance between the
front lens of the objective & the object
on the slide.
 Working distance easily determined by
noting the number of complete turns of
the microscope to raise the object
from the surface of slide.

11. Resolving power
 It is defined as the ability to distinctly
separate two small elements in the
structure of an object that are a short
distance apart.
 Resolving power is expressed
quantitatively as the microscope’s limit
of resolution (LR).

12. Numerical aperture(NA)
 It is defined as the simply diameter of
the lens to its focal length.
 It is expressed mathematically as..
NA = n sin ø
Where,
n = refractive index of the medium
between object & objective.

13. Phase- Contrast Microscope
 Phase contrast microscope is an optical-
microscopy technique that converts
phase shifts in light passing through a
transparent specimen to brightness
changes in the image.
 Phase contrast microscope discovered
by Fritz Zernik.
 In 1953 he won the Nobel prize in
physics.

14. Image of Phase-contrast microscope

15. Construction & Working
 In phase contrast microscope has a special
type of diaphragm consisting of an annual
stop.
 The annular stop allows only a hollow cone of
light rays to pass through the condenser.
 Ii is also consist of phase plate.
 Phase plate has a special ring coated with a
material that can retard the direct rays or
undiffracted rays & are unaltered in amplitude
& phase.
 Then those rays are bend & slowed down due
to difference intensity of medium are called
diffracted rays.

17.  The condenser of a phase-contrast
microscope has an annular stop, an opaque
disk with a thin transparent ring, which
produces a hollow cone of light.
 As this cone passes through a cell, some
light rays are bent due to variations in density
and refractive index within the specimen and
are retarded by about 1/4 wavelength.
 The diffracted light is focused to form an
image of the object.
 Undiffracted light rays strike a phase ring in
the phase plate, a special optical disk located
in the objective, while the diffracted rays miss
the ring and pass through the rest of the plate.

18.  Finally all rays means undiffracted &
diffracted rays come together by an eyepiece
lens.
 This type of microscopy is called dark-
phase-contrast microscopy.
 Phase-contrast microscopy is especially
useful for studying microbial motility,
determining the shape of living cells, and
detecting bacterial components.

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