I am future microbiologist Payal jain.Recently pursing M.sc microbiology in B.lal institute of biotechnology.

1. ELECTRON MICROSCOPY

2. Introduction and Histroy
 The word Microscope is derivrd from the
Greek mikros(small) and skopeo(look at).
 Dutchman Anton van leeuwenhoek
introduced simple microscope.
 Microscope magnify and resolve images.
 Dr.Ernst ruska developed first time electron
microscopy.

3. Types of Microscopy
1. Light microscopy
2. Electron microscopy

4. LIGHT MICROSCOPY
BY THE USE OF LIGHT
BEAM
1. Convex lens
2. Codenser
3. Illumination lamp
4. Eyepiece
5. Nosepiece
6. diaphram
1. Cannot studied detailed
structure of microorganism
Parts
Limitati
on

5. • An electron microscope uses an ‘electron beam’ to produce
the image of the object and magnification is obtained by
‘electromagnetic fields’; unlike light or optical microscopes, in
which ‘light waves’ are used to produce the image and
magnification is obtained by a system of ‘optical lenses’.
• an electron microscope can resolve objects as small as 0.001µ
(=10 Å), as compared to 0.2µ by a light microscope. Thus, the
resolving power of an electron microscope is 200 times
greater than that of a light microscope.
Principle of ELECTRON MICROSCOPY

7. WorkingPrinciple of transmission electron
microscopy
• In this microscope, an electron beam from an electron gun is
transmitted through an ultra-thin section of the microscopic object
and the image is magnified by the electromagnetic fields. It is used
to observe finer details of internal structures of microscopic objects
like bacteria and other cells.
• The specimen to be examined is prepared as an extremely thin dry
film or as an ultra-thin section on a small screen and is introduced
into the microscope at a point between the magnetic condenser
and the magnetic objective
• The point is comparable to the stage of a light microscope. The
magnified image may be viewed on a fluorescent screen through an
airtight window or recorded on a photographic plate by an in-built
camera. Modern variants have facility to record the photograph by
digital camera.

8. CONTENTS
Electron gun:it consists of tungsten filamentor
Cathode it is electrthat emits electron on receiving high voltage
electric current.
Ray tube: it is high vaccum metal tube (mt high)
through which electron travel
Condenser lens: it is the electromagnetic coil
which produces the first magnified image
formed by the objective lens and produces
the final image .
Objective lens: it is electromagnetic coil which
produces the first magnified image formed by the
Objective lens and produces first image.
Projector lens: it is also an electromagnetic coil
which further magniflies the first image formed
by the objective lensand produce final image.
Fluoroscent screen for viewing image

11. Working principle of Scanning electron microscope
• In a scanning electron microscope, the specimen is exposed to a
narrow electron beam from an electron gun, which rapidly moves
over or scans the surface of the specimen (Figure 4.13). This causes
the release of a shower of secondary electrons and other types of
radiations from the specimen surface.
• The intensity of these secondary electrons depends upon the shape
and the chemical composition of the irradiated object. These
electrons are collected by a detector, which generates electronic
signals. These signals are scanned in the manner of a television
system to produce an image on a cathode ray tube (CRT).
• The image is recorded by capturing it from the CRT. Modern
variants have facility to record the photograph by digital camera.
This microscope is used to observe the surface structure of
microscopic objects.

12. Contents
• Electron source
• Lenses: a series
• of condenser lenses
• focus the electron beam
• as it move
• from the source down the column.
• Scanning coil: After the beam is focused
• ,scanning coils are used to deflect the beam.
Sample chamber
• Detectors