its about the microscopes types and there significance in the world for diagnostic purposes .advantages and disadvantages of the types of different microscopes

1. Microscopy and its
significance
NAME : ROHAMA
ROLL NO : 24

2. Phase contrast microscopy
 It was developed by the Dutch physicist Frits Zernike in the 1930s.
 It is used for studying unstained cells.
 It uses light microscope fitted with phase contrast objective and phase contrast
condenser.
 It distinguish unstained parts of cell which differ in their refractive indices and
thickness.
 It is widely used in theoretical biological studies.

3. Principle
Based on the fact
light passing through one material and into
another material of different
refractive indices and thickness
will undergo a change in phase
these differences are regulated into variations in brightness
They are detectable by eye

4. Advantage
 Possible to reveal differences in cells.
 Reveal differences in their structures.
 Not possible by other microscopes.

5. Fluorescence microscopy
 Application of fluorescence phenomena is the basis of fluorescence microscopy.
 What is florescence?
chemicals absorbing emitting light of
light of shorter wavelength longer wavelength
and high energy and less energy
 Microorganism is stained with florescent dye
 Illuminated with blue light and green light is emitted

6. Fluorescent antibody technique
Fluorescent dyes + Antibodies
labeled antibodies
+
suspension of bacterial cells
examined with fluorescence microscope
 By this it is possible to identify the single bacterial cell.
 Application of this test in diagnostic procedures.

8. Transmission electron microscope
 The transmission electron microscope (TEM) uses a high voltage electron beam to
illuminate the specimen and create an image.
 It provides high resolution due to shorter wavelength.
 It is possible to resolve objects as small as 10 angstrom
 Its resolving power is 100 times more than of light microscope.
 Its magnification is x 400,000.

9. working
 Specimen to be examined is prepared in thin dry films.
 The electron beam is produced by an electron gun, commonly fitted with a
tungsten filament cathode as the electron source.
 Slide is introduced between magnetic condenser and magnetic objective
Magnified image
Airtight window by a camera
On fluorescent screen on photographic plate

11. Scanning electron microscope
The SEM produces images by probing the specimen
with a focused electron beam
that is scanned across a rectangular area of the specimen
the electron beam interacts with the specimen
energy loss
heat, emission of low-energy secondary electrons and high-energy
back scattered electrons or x-ray emission
all of them carries information about the properties (specimen)

13. Stereo microscope
 It is variant designed for low magnification observation of a sample.
 Using light reflected from the surface of an object rather than transmitted through
it.
 The instrument uses two separate optical paths with two objectives and
eyepieces to provide slightly different viewing angles to the left and right eyes.
 This arrangement produces a three-dimensional visualization of the sample
being examined.

15. Significance
 Microscopes help the scientists to study the microorganisms , the cells
crystalline structures and the molecular structures .
 Microscopes magnify the blood samples , so , The doctors can see the malaria
parasites attacking the red blood cells .
 Scanning electron microscopes have the magnifications up to several million times
to view the molecules , the viruses and the nano-particles.
 Microscopes enlarge the images of silicon chips to help the engineers create
more efficient electronic devices .
 All branches of biology uses Microscopes especially in Molecular Biology and
Histology ( study of cells ) .

16.  Microscopes are used to diagnosis the illness in the hospitals and the
clinics all over the world
 By using Microscopes scientists were able to discover the existence of
the microorganisms , study the structure of cells , and see the smallest
parts of plants , animals , and fungi .
 Microscopic examination confirms the laboratory tests that may be
positive for the disease.