To study working of compound microscope .docx

microscope

1. Experiment No.
Aim: To study the working of compound microscope.
Reference: Khandelwal, K.R; Sehi, V.K; Practical book of Pharmacognosy, Nirali
Prakashan, Edition 23
rd
, Page no. 1.1-1.2.
Requirements: Compound Microscope
Theory: Microscope is an optical instrument for the study of small objects. The compound
microscope is composed of mechanical and optical units and essentially consists of following
parts:
a) A lens system
b) Provision for focusing the lens system.
c) Stage
d) Device for providing satisfactory.

1) Eye piece: The function of eye piece is to magnify the image. The eyepiece normally ranges
in magnification from x5 to x15.
2) Draw tube: To fit the eye piece inside.
3) Body tube: It is cylinder holding the draw tube and lenses and moves up and down vertically
above the hole in the stage.
4) Coarse adjustment knob: The body tube is raised or lowered by the coarse adjustment knob
and is used to bring the object into focus.
5) Fine adjustment knob: For fine of clear focus of specimen to reveal finer characteristics in
detail.

Compound microscope


6) Multiple nose piece: Hold 2,3,4 objectives which can be resolved to align the required object.

2. 7) Stage: To hold the object on slide.
8) Slide holder: To hold the slide.
9) Arm: To hold the microscope while handling.
10) Condenser: Condenses the light and allows parallel beams of light to pass through the stage
aperture.
11) Mirror: Reflects light through the substance condenser and stage aperture on to the object.

**


Working Procedure:

1) Place the microscope on the table with the arm.
2) Turn the lowest power objective into position.
3) Find the light by looking into the eyepiece and at the same time turn the mirror at such an angle
that it reflects light from the window or lamp up through the hole in the stage to the objective.
4) Place the prepared slide in the slide holder on the stage in the horizontal position with the object
right in the center of the hole through which light is reflected from the mirror.
5) Make the lower power objective quite close to the slide by turning the coarse adjustment knob
down.
6) Then while looking through the eyepiece, move the coarse adjustment knob upward until the
object is seen distinctly.
7) The object, if not under the lens, may now be brought into the field by moving the X-Y
movement very slowly while looking through the eyepiece.
8) Then slowly turn the fine adjustment knob to improve the focus.
9) Regulate the quantity of light with the iris diaphragm to improve the clarity of the field.
10) To focus with the high power objective, first find the object with the low power and arrange in
the center of the field.
11) Raise the lower power objective by means of coarse adjustment knob.
12) The turn the high power objective into position and lower until the objective front lens nearly
touches the glass.
13) A slight movement of the fine adjustment knob should show the object clearly.
14) Never try to focus with the high power objective while looking through the eyepiece because of
the danger of breaking the cover glass and damaging the tissues lying underneath. It may also
cause damage to the delicately mounted lenses.


Magnifying Power = Magnification of Objective lens X Magnification of Eye piece

3. Instructions for use of Microscope:

1) It should be handled carefully.
2) Keep the microscope free from dust.
3) Avoid touching the microscope with wet fingers.
4) Do not allow any liquid to get on to the tissue or the stage.
5) Place the microscope in upright position at a convenient height facing the source of light being
used.

Result: The working of compound microscope has been studied.