Microscope

A microscope is an instrument used to observe very small organisms i.e. microorganisms. The microscope provides magnification and resolution which makes the image enlarged and fine. There are different types of microscopes ranging from simple to compound microscopes.

1. Microscope
Anup Muni Bajracharya

2. What is microscope?

•"Micro" refers to tiny,
•"scope" refers to view or look at.

Microscopes are tools used to enlarge small
objects so as they can be observed and
studied.
Microscopes range from a simple magnifying
glass to the expensive electron microscope.

3. History of Microscopes

•Timeline of the Microscope
•14th century: spectacles first made in Italy

•1590: Two Dutch spectacle-makers and father-and-son team, Hans
and Zacharias Janssen, create the first microscope.

•1667: Robert Hooke's famous "Micrographia" is published, which
outlines Hooke's various studies using the microscope.

•1675: Anton van Leeuwenhoek, who used a microscope with one
lens to observe insects and other specimen. Leeuwenhoek was the
first to observe bacteria.

•1830: Joseph Jackson Lister discovers that using weak lenses
together at various distances provided clear magnification.

4. •1878: A mathematical theory linking resolution to light
wavelength is invented by Ernst Abbe.

•1903: Richard Zsigmondy invents the ultra microscope,
which allows for observation of specimens below the
wavelength of light.

•1932: Transparent biological materials are studied for
the first time using Frits Zernike’s invention of the
phase-contrast microscope.

•1938: Just six years after the invention of the phase
contrast microscope comes the electron microscope,
developed by Ernst Ruska, who realized that using
electrons in microscopy enhanced resolution.

•1981: 3-D specimen images possible with the invention
of the scanning tunneling microscope by Gerd
Binnig and Heinrich Rohrer.


History of Microscopes

Ernst Ruska

5. Classification of Microscopes
Simple microscope Compound microscope
1. It has a single lens system. 1. It has two or more lens system.
2. Eg:-Magnifying glass. 2. Eg:-Compound microscope
basically used in the laboratory.
Microscope can be classified on the basis of various properties.
On the basis of lens system, microscopes are of two types.

6. Light Microscope Electron Microscope
1. It uses light as a source of
illumination.
1. It uses electron or electron gun as a source of
illumination.
2. Lens used in glass lens 2. Lens used is electromagnetic lens.
3. Here, vacuum is not needed. 3. Vacuum must be created since electrons can
travel only in vacuum.
4. Resolution is low comparing to the
electron microscope.
4. Resolution is very high capable of viewing
particles of size 0.1 to 0.2 nanometer (nm).
5. Image can be directly seen by human
eye.
5. Since, electrons can’t be seen by human eye.
Electrons are converted into an amazing image by
striking in fluorescent screen.
Classification of Microscopes

8. Types of Microscopes
A.B

9. Bright-Field Microscopy

The standard instrument used in the
laboratory to observe microorganisms is the
bright field compound microscope.
In bright field microscopy, the microscopic field
is bright and the microorganisms appear dark
because they absorb some of the light.

10. Principle of Microscopy
•1. Magnification
The microscope produces an enlarged image of the
object which is examined through it. This enlargement is
known as its magnification and is measured in diameter
•Eg: A magnifying lens which gives an image 36 time as
large as that of the object is said to have a magnification
of 36 diameter or 36X(x=times).

11. Which of these images would
be viewed at a higher power of
magnification?
1.Magnification
We can see better details with higher the powers
of magnification, but we cannot see as much of
the image.

12. Total Magnification

13. Fill the gaps….

14. 2. Resolution
•The ability of microscope to distinguish two closely spaced
objects as separate and distinct entities called resolution.

• Eg. The human eyes has the resolving power of 0.25mm
which means that two dots is placed 0.25mm apart can be
distinguished as two dots.
•If the distance between the two dots is less than 0.25,only
one dot will be seen.

•Resolving Power(R.P.) =
�
2.�.�
whereλ wavelength
of light ,N.A=Numerical Aperture

15. Resolution : Resolution is the quality of image that is measured
by the smallest distance which could be seen clearly without
the blur due to diffraction.

Resolving power :
The ability of an optical instrument to separate or distinguish
small or closely adjacent objects through the image formation
is said to be resolving power of the instrument.

18. Oil immersion
•Immersion Oil is a special oil used
in microscope work with the
highest power objective lenses (ie
100x lens).

•In light microscopy, oil
immersion is a technique used to
increase the resolving power of
a microscope.

•This is achieved by immersing
both the objective lens and the
specimen in a transparent oil of
high refractive index, thereby
increasing the numerical
aperture of the objective lens.

19. Immersion Oil and Refractive Index

20. Microscope

21. Parts of Microscope
•Body: the portion of the microscope
which contains the lenses.
•Revolving Nosepiece: the assembly
which contains the objective lenses.
•Stage: the platform upon which the
object to be examined is placed

•Sub-stage Assembly: the parts below
the stage; these include the condenser,
iris diaphragm, and illuminator.


•Condenser Lens: a lens assembly
beneath the stage which concentrates
light on the object being examined.
•Diaphragm: a series of holes which
control the amount of light which
reaches the object being examined.

22. •Coarse and Fine
Adjustment Knobs: these
knobs adjust the distance
between the objective lens
and the stage. This distance
is called the working
distance.

•Illuminator: the light
source. It may be built into
the base or it may not be
part of the scope at all.


Parts of Microscope
COARSE ADJUSTMENT KNOB —
rapid control which allows for
quick focusing by moving the
objective lens or stage up and
down. It is used for initial focusing.

FINE ADJUSTMENT KNOB —
Slow but precise control used to
fine focus the image when viewing
at the higher magnifications.

23. Handle and care of Microscope
Always keep your microscope covered when
not in use even if the microscope is stored in a
cabinet.

Always use two hands when moving the
microscope. When carrying your microscope,
hold it by the base and the metal support arm.

24. If using immersion oil, always ensure the objectives are cleaned
immediately after use. Objective, eyepieces and condenser may be
removed for cleaning. Use only lens paper and lens cleaner.

25. Turn the microscope off after use.
Do not keep the light on all day as this will
shorten the bulb’s life.