Monday, June 4, 2012

How does a Microscope Work?

            A microscope is an optical instrument that is used for viewing very minute objects, which cannot be seen by the naked eye. Simple microscope or magnifying glass comprising of a single converging lens was known is ancient times. But the first compound microscope was invented by a Dutch spectacle maker, Zacharias Janssen, around 1590. Compound microscopes using ‘achromatic’ lenses were made in the 1840s.

The different parts of a Microscope

            In simple words, microscope is an instrument used for producing enlarged images of very small objects. Today microscopes are used to see magnified images of bacteria, cells of living beings and many other minute objects and study their structures. Do you know how a microscope produces enlarged images?

            A microscope consists of two convex lenses of short focal length fitted at the two ends of a hollow tube. The lens towards the object is called the object lens ad has a very small focal length. The other lens positioned towards the eye is called the eye-piece and has a large focal length. The object under observation is placed on a platform of the microscope close to the object lens, which makes an enlarged real image. This very image acts as an object for the eye lens, which in turn makes an enlarged virtual image. It is this virtual image that is formed on the retina of the eye.

            Microscope can magnify an object up to 1000 times its actual size or even more. Since these instruments use light for illuminating the object, they are called optical microscope.

            In electron microscope beams of electrons are used rather than light to study objects too small for conventional microscopes. It is also used for structural defects and composition studies in a wide range of biological and inorganic materials.

            The various lenses of the electron microscope allow the operator to see details of an object magnified almost up to a million times. However, many specimens may deteriorate under the electron beams.