what is a microscope?
Microscope : An instrument through which minute objects are enlarged by means of a lens or lens systems. Principles types would include optical microscopes, electron microscope and X- ray microscopes.
Most commonly used microscope is the compound microscope and it consists of three types of lens systems
1. Condenser lens systems: It occurs beneath the the specimen and its function is the collection and focussing of the light rays on the object or specimen which is placed on the stage of the microscopes.
2. Objective lens system remains near and above the specimen. It produces and magnifies the image of the specimen.
3. Eye piece lens system or occular lens system remains near the eye of the observer and it magnifies and forms the image (secondary of the primary image) previously produced by the objective.
what is a electron microscope: The first electron microscopes was designed by knoll and Ruska of Germany in 1932. In this microscope a beam of electrons is used to resolved objects smaller than 2000 amstrong , as such small objects can not be resolved using light microscope.
The electrons emitted by a heated metal filament placed in vacuum are collected and focussed on the object by an electromagnetic condenser lens. After the electrons are passed through the object, they are collected again by an electromagnetic coil which acts as objective lens. This lens produces a magnified image of the object which is received by a third electromagnetic lens which in turn, acts as an occular or projection lens. The projection lens magnifies the image formed by the objective lens. The final image can be visualised on fluorescent screen or can be recorded on photographic plate. Two types of electron microscopes are used in cytological studies: Transmission electron microscope and scanning electron microscope.