This document discusses dark field microscopy. It explains that dark field microscopy allows the observation of unstained living cells and organisms by illuminating the specimen in a way that only light reflected or refracted by the specimen forms the image. The field surrounding the specimen appears dark while the object is brightly illuminated, allowing internal structure of larger microorganisms to be revealed. Some common uses of dark field microscopy include studying unstained, transparent samples like insects, fibers, yeast, and bacteria, as it is useful for examining external details like outlines. Dark field microscopy is often combined with other illumination techniques to widen its applications.

1. DARK FIELD
MICROSCOPY

2.  Dark field microscopy allows viewer to
observe living unstained cell and organisms
simply by changing the way in which they
illuminate the object.
 A hollow cone of light is focused on the
specimen in such a way that unreflected and
unrefracted rays do not enter the objective.

3.  Only light that has been reflected or
refracted by the specimen forms the image
 The field surrounding specimen appears
dark while the object brightly illuminated.
 The dark field microscope can reveal
considerable internal structure in larger
eukaryotic microorganism.

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USES OF DARK FIELD
MICROSCOPY
 Unstained, transparent and absorb little or no light.
 To study insects, fibers, hairs, yeast and protozoa as well
as some minerals and crystals, thin polymers and some
ceramics.
 In the research studying of live bacterium, as well as
mounted cells and tissues e.g. Treponema pallidum,
Leptospira, Vibrio cholera, Campylobacter jejuni,
Endospore
 It is more useful in examining external details, such as
outlines, edges, grain boundaries and surface defects than
internal structure.
 Recently, dark field combined with other illumination
techniques, such as fluorescence, which widens its
possible employment in certain fields.

9. BRIGHT FIELD VS.DARK FIELD
MICROSCOPY

11. Advantages
 The advantage of darkfield microscopy also
becomes its disadvantage: not only the
specimen, but dust and other particles
scatter the light and are easily observed
 For example, not only the cheek cells but the
bacteria in saliva are evident.
 The dark field microscopes divert illumination
and light rays thus, making the details of the
specimen appear luminous.

12.  Dark field light microscopes provide good
results, especially through the examination of
live blood samples.
 It can yield high magnifications of living
bacteria and low magnifications of the
tissues and cells of certain organisms.
 Certain bacteria and fungi can be studied
with the use of dark field microscopes.

13. THANK