Botany practical Experiment No 1

                              EXPERIMENT NO : 1

TITLE:STUDY OF A COMPOUND MICROSCOPE

       A compound  microscope is a delicate optical instrument consisting  of two lens system [eye piece and objective lens] that magnifies the minute transparent or translucent object manifold in two steps and enables us to study their minute details.This two fold magnification is the principle behind the working of compound microscope.The compound monocular microscope consists of many parts,or optical parts.

Mechanical parts of a compound Microscope.

1.Foot:-It is usually a horse-shoe shaped lowermost part.It supports the weight of the microscope.

2.Pillar:-It is a small vertical stand attached to the base.It supports the movable parts.

3.Inclination joint:-It is a pivot between the pillar and the arm.It permits the tilting of the upper part of the compound microscope at various  angles.

4.Arm:-It is a curved part of a microscope and its lower end is attached to the pillar and upper end is joined to the body tube.It is used for handling.

5.Condenser:-It is a circular chamber with the lens system present below the stage that can be raised or lowered .It is used to concentrate the light rays .

6.Iris diaphragm:-It is a circular piece with a knob below the condenser.The left and right movements  of the knob control the amount of light entering into the microscope on the object.

7.Stage:-It is usually a rectangular platform having a circular hole in the center to allow the light to pass  through.It is used for keeping an object to be magnified.

8.Clips:-There are two clips attached to the stage one on each side.These are used for holding the glass slide onto the stage firmly.

9.Nose piece:-It is a revolving circular disc-shaped metallic structure attached below the body tube.Generally three objective lenses are screwed to it.

10.Draw tube:-It is a hollow cylindrical metallic tube that supports the eye piece at the top.

11. Body tube:-It is a hollow cylindrical metallic tube attached at the upper end of the arm carrying draw tube above and nose piece below.

12.Coarse adjustment:-It is large sized screw attached at the upper and of the arm.It can be moved up and down to bring th object into rapid focusing under low power.

13.Fine adjustment:-It is small sized screw and also attached to the body tube.It helps in the adjustment of the sharp focusing.It is used when the object is under high power.

Optical parts of a compound microscope

1.Mirror_-It is a plane-concave mirror, with one side plane and other concave.It is attached to the lower end of the arm.It is used for reflecting light rays into the microscope.The plane  Mirror is used to reflect the rays of light coming from nearby sources such as bulb or tube light while the concave mirror is used to reflect the rays of light form distant source i.e the diffused sunlight.

2.Objective lenses:-They are attached to the nose piece.Generally the lenses with the magnification power of 5X, 10X, 40X and 100 X are available.These lenses magnify the image of the object bye the number written on the lens.

3.Eye piece lens:-It is also called ocular lens and attached to the top of the body tube.It  normally ranges in the magnification from 5X, 10X and 15X. It is used  to magnify the image produced by the objective.

Magnification of object

 A microscope magnifies an object in two stages.The lens system magnifies the object 5 to 100 times depending on the power of the objective lens.The ocular lens magnifies an object 5 to 15 times. The  individual magnification power  of the ocular or objective is written on the outside of its barrel.To calculate the total magnification the image with each objective,use the following equation:

Total magnification:Magnification of the objective lens + Magnification of eye pieces.

Handling of compound microscope

1.The microscope was placed on the table by holding arm at the back with one hand and base with other hand.

2.The lower power objective was fixed and the mirror was adjusted so that light may pass through the objective.

3.A slide was gently placed with the specimen over the stage and clips were used to hold the slide firmly .

4.Looked through the eye piece and adjusted with the help of coarse adjustment until the object come in view.

5.An object was focused fine and sharp with the help of fine adjustment.