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FORMATION OF THE IMAGE
It
is the lenses composing the objective which initiate the magnifying process. An
objective operates at a distance from
the object that is roughly equal to its focal length, and admits rays that are
to form a real, an inverted, enlarge image in the upper part of the tube. At
this point, there is interposed another lens, the field lens whose function is
to collect the diverging rays of the primary image so that they may pass
through the eye lens of the piece which magnifies the image still further. The
field lens is accommodated in the lower plane of the eye piece. Rays, as they
leave the eyes piece to reach the observer’s eye, are once more divergent and
thus the image seen by the retina is virtual, appearing to be about 25 cm (10
inches) in front of the eyes.
Formation of The Image is three types :-
A. Magnification
B. Resolution
C. Oil
Immersion Objective
A. Magnification :- The magnification of the object is determined by multiplying the power of the Objective
(X inscribed on the objective or eye piece denotes the Unit of the Magnification).For example, if the eye piece
magnification is 10x and that of objective lens is 100x, then a given object
gets magnified by 1,000 times.
C. Oil
Immersion Objective:- Oil immersion objective is most frequently used in Haematology
because of its Greater Magnification and Resolution.
It
has been seen that any factor which reduces the amount of rays falling on the
objective, impairs the quality of the image. In case of oil immersion
objective, the space between the object and the objective lens is filled with
some transparent fluid (such as liquid paraffin, glycerin or transparent oil) with the same
refractive index as glass (=1.515)
then the rays of light do not undergo refraction
and pass directly into the objective. The most commonly used fluid is the cedar wood oil
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