► Improvements in the microscope and
development of related biological techniques made
our present knowledge of cell structures and
► The compound light microscope is the major
instrument for the study of cells. It will be
used in the laboratory and can provide
magnification up to 500X, depending on the
magnification of the ocular and the objective.
► Although some compound light microscopes
can provide a magnification of 2000X, there
is a limitation to the magnification, due to
the resolving power of the lens.
► Therefore, the compound light microscope
is primarily useful for viewing large cell
organelles, such as nuclei and
The compound light microscope
has 2 lens combinations:
A. The objective lens which forms a
magnified image of the specimen.
B. The ocular lens or eyepiece lens,
which further magnifies the image.
The specimen used on the
compound light microscope must
There are a number key parts of the
compound light microscope and the
functions of these parts are as
1. Ocular lens (eyepiece): used to “look
through” and generally magnifies at 10X.
2. Objective lenses: found closest to the
object to be studied. It provides the rest
of the magnification of the compound light
microscope and generally magnifies at 4X,
► Magnification of a compound microscope is
the product of the power of the objective
multiplied by the power of the ocular.
objective = 40X
Ocular = 10X
What is the total magnification?
► Useful magnification is limited by its
► The resolving power is the ability to
separate 2 objects close together.
► The properties of light place an upper limit
on the resolving power of any light
►The flat surface (platform) on
which the specimen or slide to be
studied is placed.
4. Stage Clips
►Used to hold the specimen or slide
5. Coarse Adjustment:
► The larger knob
► Used primarily to focus under low power (up
to 100X) only!
► It causes large movement of focusing.
► Course adjustment must never be used
when the high power objective is in
► If you use this under high power, you will
break the slide!!!!
6. Fine Adjustment:
►The smaller knob
►Used for focusing under high power
and final focusing under low power.
►It causes small movement for focusing.
►The fine adjustment knob should never
be turned more than one half turn in
7. Light Source:
► Provides light
► Light must pass through the object to be
studied in order for an image to be viewed
in the objective lens.
► In some microscopes, a mirror is present
and directs the light from a horizontal
surface up through the diaphragm and the
►It is found under the stage.
►Controls the amount of light passing
through the specimen and into the
►Smaller openings of the diaphragm
increase the resolution or the amount
of detail in the image.
►Holds the tube and the stage
►Used to carry the instrument
►Supports the instrument
11. Body Tube
►Hold the lenses
►Rotates to change the objective
lens from one power to another.