Study of Microscope Its Parts & Functions

                              STUDY OF MICROSCOPE                             

Microscope is the most commonly used piece of apparatus in the laboratory. Human eye can see up to ~ 0.1mm. Bacterial size ranges from 0.2 to 5 µm. Microscope can produces greatly enlarged images of minute objects of 0.2 µm and above and to see objects below this size electron microscope is used. Common light microscope is described first, followed by other special types of microscopy techniques.

Principle

The principle of microscope is to show large images of those objects which cannot be seen with the naked eye.

Light Microscope

It is used in laboratory, it has a wavelength of 0.4 µm & its resolutions is 0.2 µm

Type of Microscope

  • Light Microscope
  • Electron Microscope
  • Fluorescent Microscope
  • Phase contrast Microscope
  • Dark field Microscope
  • Laser Microscope

Parts of Microscope

A compound microscope has the following parts:

  • Stand
  • Body
  • Optical system
  • Light/illumination system

Stand

This is horse-shoe shaped in monocular microscope. It gives stability to the microscope. Binocular microscopes have a variety of ergonomic shapes of stand.

MicroscopeLabeled

Microscope  Labelled

Body

It consists of a limb which arises from the joint with which microscope can be moved in comfortable position. The stand and the limb carry the following:

i.            Body tubes

ii.            Stage

iii.            Knobs for coarse and fine adjustment

Body tubes

There are two tubes: external tube which carries at its lower end a revolving nose piece having objective lenses of different magnification while internal tube is draw tube which carries at its upper end eye pieces.

Stage

This is a metallic platform which accommodates glass slide having mounted object over it to be seen. Stage is attached to the limb just below the level of objectives. It has an aperture in its centre which permits the light to reach the object. Slide on the stage can be moved horizontally or vertically by two knobs attached to slide holder. Just below the stage is substage which consists of condenser through which light is focused on the subject. The substage can be moved up and down. The substage has an iris diaphragm, closing and opening of which controls the amount of light the object.

Knobs for coarse and fine adjustment

For coarse and fine adjustment, knobs are provided on either side of the body. Coarse adjustment has two bigger knobs, the movement of which moves the body tubes with its lenses. Fine adjustment has two smaller knobs on either side of the body. The fine focus is graduated and by each division objectives moves by 0.002 mm.

Optical system

Optical system is comprised by different lenses which are fitted into a microscope. It consists of eye piece, objectives and condensers.

Eye piece

In monocular microscope, there is one eye piece while binocular microscope has two. Eye piece has two plano convex lenses. Their magnification can be 5×, 10×, or 15×.

Objectives

These are made of a battery of lenses with prisms incorporated in them. Their magnification power is 4×, 10×, 40× and 100×.

Condenser

This is made up of two simple lenses and it condenses light on to the object.

Comments:

1 mm = 10 3 µm

1 µm = 10 3 nm

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