Study of compound microscope

 

AIM : Study of compound microscope

INTRODUCTION :A compound microscope is a type of microscope that uses two sets of lenses to magnify the image under the microscope. it has an objective lens that has a resolution of 4x,10x, 40x, 100x, and an eyepiece of resolution of 10x. the usage of both lenses, compounds or magnifies the image of the object below the objective lens to achieve a resolution of 40x, 100x, 400x, 1000x.

Parts of the compound microscope may be grouped into two major categories

 

Ø  Mechanical parts

Ø  Optical parts.

 (a)  Mechanical Parts:

 These include base or foot, pillar, arm, inclination joint, stage, clips, diaphragm, body tube, nose piece, coarse adjustment knob and fine adjustment knob.

(b)  Optical Parts:

 

These include eye piece lens, objective lenses and mirror. All these parts are briefly described below:

1. 

Foot or Base: It is the basal, horse shoe-shaped structure. It provides support to all the remaining parts of the microscope.

 Pillar: A small, strong vertical projection   developing from the foot or base is called pillar.

 Arm: It is a curved and strong structure used for handling the entire instrument.

Inclination Joint: A joint at which the arm is attached to the pillar of the microscope is called inclination joint. It is used for tilting the microscope.

Stage: It is a flat rectangular plate attached to the lower end of the arm. Slide or object is placed on the stage and studied. A hole is present in the centre of the stage. Light rays pass through this hole.

 Clips:Two clips are attached on the upper part of the stage. These are used for holding the slide in position.

 Diaphragm: It is attached beneath the stage. It regulates the intensity or amount of light entering into the microscope. It may be of two types viz., iris diaphragm and disc diaphragm.

Condenser: It is a lens situated beneath the stage. It controls the size of the light beam. It gathers light from the mirror (Fig. 279) and directs it to objective lens. Condenser may be lowered or raised by a knob present on one side beneath the stage.

 Body Tube: It is the tubular, hollow part attached to the upper part of the arm of microscope. It can be moved up and down with the help of adjustment knobs.

Nose Piece: It is a circular and revolving metalic part attached to the lower end of the body tube. It has three holes in which objective lenses can be fitted.

Coarse Adjustment Knob: It is a large-sized knob used to move the body tube up and down for bringing the object into focus.

Fine Adjustment Knob: It is a small-sized knob. It is used for fine and sharp focussing of the object. Exact focussing is done by this knob.

Optical parts

1.  Eyepiece or Ocular: It is a lens fitted at the top of the body tube. It is always marked with a number (5X, 10X, 15X) on its rim. This number shows its magnification power. Magnified image of the object is seen with the eyepiece.

2.  Objective Lenses: Three objective lenses are attached to the revolving nose piece at the bottom of the body tube. These are low power objective (10X), high power objective (45X) and oil immersion objective (100X).

3.  Mirror:: It is either attached to the lower end of the arm or to the pillar. It contains a plane mirror on one side and a concave mirror on the other side. Mirror is used to reflect light rays into the microscope.