NAME: NAVERA ZAHEER
CLASS: BS IV YEAR
TOPIC:MICROSCOPY (LIGHT MICROSCOPY)
SUBMITTED TO: Dr. FARAH TARIQ
An instrument which is used to observed organisms ,which are
not been able to see with our naked eyes.
It is used for viewing objects such as micro organisms which
are too small to be visible with human eyes. It is an important tool in modern era
for the visualizing of the microbial world the choice of microscope depends
upon the size of the object, nature of specimen, and all the purposes of the
Firstly, ROBERT HOOKE an English Scientist invented an
optical microscope in 1665.The main purpose is to visualize biological
specimen. After 10 years ANTON VON LEEUWENHOEK invented a simple glass lens of
convex surface. The main purpose is to observed bacteria, fungi, blood cells, plants,
protozoa etc.Then after Ernest Abbe in 1870 intenvetd compound microscopy. The
main purpose is to create microscope lens that helps to create much magnified
and fine image.
OIL IMMENSE LENSES:
Oil immense lenses are used in microscope; allow improving
resolution and classifying image.
10X Low power lenses , used for
40X High power, used for
100X Oil immersion lenses, used for
bacteria except viruses
Microscopes are classified in various branches, which are as
Bright field microscopy
Dark field microscopy
Phase contrast Microscopy
Transmission Electron Microscope
Scanning Transmission Electron Microscope
LIGHT FIELD MICROSCOPY:
Light is directly passed through a specimen
that may be stained or unstained .It has a single len which is used to
magnified image with low magnification.
It formed image when light is transmitted
through the specimen.
Specimen being dense and more opaque then its
surrounding observed some of this light, the rest of the light is transmitted
directly up through the ocular into the field.
Specimen should be
examine by BFM are protozoan cell E.g. Amoeba,
As a result specimen
produced as image that is darker than its surrounding with brightly illuminated
It is a multipurpose instrument that can be used for both alive ,unstained
materials ,and preserved stained materials.
DARK FIELD MICROSCOPY:
microscopy can be adapted as dark field microscopy by adding a special disc
called stop to the condenser.
The stop blocks all the light from entering into the objective lens except
peripheral light i.e. referred as the light reflected off the sight of the
specimen its self. The resulting image is particularly stricken one i.e. bright
illuminated specimen surrounding by a dark filed.
Ø The most effective
use of DFM is to visualize living cell that could be distorted by dying or heat
or can’t be stain with the visual method.
Ø It can outline the
organism shape and permit rapid identification of swimming cell that might
appear in dental and other infections.
Ø It can’t reveal fine