An electron microscope uses a beam of accelerated electrons rather than light to illuminate samples, allowing it to achieve much higher magnifications than an optical/light microscope. There are two main types - transmission electron microscopes look through thin samples, while scanning electron microscopes examine surface features. Electron microscopes can reveal ultrastructures as small as angstroms in size and are widely used to study cells, biomolecules, and inorganic materials.

2.  An electron microscope is a microscope
that uses a beam of accelerated electrons as
a source of illumination.
 As the wavelength of an electron can be up
to 100,000 times shorter than that of visible
light photons,
 electron microscopes have a
higher resolving power than light
microscopes and can reveal the structure of
smaller objects.

3.  Electron microscopes are used to
investigate the ultrastructure of a wide
range of biological and inorganic
specimens
including microorganisms, cells,
large molecules, biopsy samples, metals
, and crystals.

4. Types
There are two main electron microscopy
techniques:
Transmission electron microscopy,
which essentially looks through a thin
slice of a specimen.
Scanning electron microscopy, which
looks at the surface of a solid object.

5. Transmission Electron
Microscope
 The Original Form of EM that uses the
high voltage Beam of Electrons to create
an image.
 Its has Resolution power up to
0.5 angstrom (50 picometres).
 Most Powerful for observing
minute objects

6. Components

7. Mechanism
 Electron Gun Produces Beam of 100 keV.
 Anode and Cathode accelerate Beam.
 Focusing occur by Electrostatic and
electromagnetic lenses
 Beam strikes the sample and pass through
it.
 After emerging out it carries information
about Sample and magnify it by objective
lens
 Information can be analyzed by Screen or
Film or CCD Cameras on LCD or monitor.

8. Advantages
 TEMs offer the most powerful
magnification, potentially over one million
times or more
 TEMs provide information on element and
compound structure
 Images are high-quality and detailed
 TEMs are able to yield information of
surface features, shape, size and structure
 They are easy to operate with proper
training

9. Limits of TEM
 High Voltage can damage Sample.
 Sample should be extremely thin upto
100 nm.
 Bio Samples are Dehydrated ,
chemically fixed, embedded in polymer
resin to stabilize them.
 Staining is required to highlight in order
to achieve require image contrast.

10. Scanning Electron Microscope
 SEM produces the image by scanning it
with focus beam of electron.
 Electrons interact with electrons in
sample and convey information in form
of signals to detectors. E.g. topography
& sample surface.
 SEM can achieve resolution better than
1 nanometer.

11. Mechanism
 When High energy Electrons strikes the
surface, it lose energy by diff.
mechanisms like heat, emission of low
energy secondary electrons and high
energy backscattered electrons.
 X-ray or light emerges from sample that
carries information on it.

12. Advantages
 Its basically used for biological samples
 It can scan the processes occurring on
surface and tells about topography and
composition.
 Enable us to view without thinning
dehydrating fixing the sample
 Can scan bulk samples upto 2-3 cm which
can not be examined by TEM.
 View obtained is in 3D.
 ESEM produce image of Wet, gas &
Vacuumed Samples and biological samples.

13. Sample preparation
1.Chemical fixation-
formaldehyde and glutaraldehyde,
and lipids with osmium tetroxide.
2. Negative stain – suspensions containing
nanoparticles or fine biological material (such as
viruses and bacteria) are briefly mixed with a
dilute solution of an electron-opaque solution.
3. Cryofixation – freezing a specimen so rapidly,
in liquid ethane, and maintained at liquid nitrogen
or even liquid helium temperatures, so that the
water forms vitreous (non-crystalline) ice.

14. disadvantages
 Electron microscopes are expensive to
build and maintain.
 The samples largely have to be viewed
in vacuum.

16. Thanks for being Patience