Microscope is an instrument which gives an enlarged view of small objects. It is used by scientists to study bacteria and other very small things which cannot be seen by the human eyes. The simplest type of microscope is the magnifying glass, a convex lens. It can make objects nearly ten times larger at its strongest point. Magnifying glasses have been used since the days of Romans of ancient Rome.
An improved type of magnifying glass named the compound micro- scope was invented in the 16th century. It enlarged a picture as much as 2,000 times. The com pound microscope has two or more lenses fixed in tubes which can slide within one another. For getting a sharp, fine, clear cut picture the tubes are moved up and down until all the lenses are in focus. Leeuwenhoek, a scientist of Holland developed a better version of microscope. Hence, Leeuwenhoek is called as “the father of the microscope”.
An optical microscope works by throwing light on the object to be viewed and seeing it by that light. Images by an optical microscope can be enlarged upto 2500 times. But, as light consists of waves of some length and very small objects are smaller than the wavelength of light, they are not visible to the ordinary light. Hence, a better and much stronger instrument named the electron microscope developed in Germany before the World War II. It solved the problem of identifying very small objects. The electron microscope is capable of magnifying images a million times and is thus, used to study micro-organisms like viruses, bacteria etc.
As light travels in the form of waves, similarly waves are also concerned with the moving of electrons. These are called matter waves and the electron microscope was built by making use of matter waves associated with electrons. Wavelengths of light waves are longer than that of the waves associated with electrons. Because of this reason the electron microscope has a greater resolving power and better magnifications in comparison to the optical microscope.
The electron microscope functions like an optical microscope with a condenser, objective and projector lenses. The lenses are strong magnets or electrodes. A beam of electrons is concentrated onto the object. With the aid of electromagnetic lenses, a magnified image of the object is made on a fluorescent screen. This image is photographed on a photographic plate and the object structure is examined in detail.