It is not definitively known who invented the microscope. However, the earliest microscopes seem to have been made by Dutch opticians Hans Janssen and his son Zacharias Janssen and by Dutch instrument maker Hans Lippershey (who also invented the telescope) about 1590.

Principlesofmicroscopy PDF

microscope, instrument that produces enlarged images of small objects, allowing the observer an exceedingly close view of minute structures at a scale convenient for examination and analysis. Although optical microscopes are the subject of this article, an image may also be enlarged by many other wave forms, including acoustic, X-ray, or electron beam, and be received by direct or digital imaging or by a combination of these methods. The microscope may provide a dynamic image (as with conventional optical instruments) or one that is static (as with conventional scanning electron microscopes).

Microscope slides are small rectangles of transparent glass or plastic, on which a specimen can rest so it can be examined under a microscope.

Principle of microscopein microbiology

The magnifying power of a microscope is an expression of the number of times the object being examined appears to be enlarged and is a dimensionless ratio. It is usually expressed in the form 10× (for an image magnified 10-fold), sometimes wrongly spoken as “ten eks”—as though the × were an algebraic symbol—rather than the correct form, “ten times.” The resolution of a microscope is a measure of the smallest detail of the object that can be observed. Resolution is expressed in linear units, usually micrometres (μm).

Principle ofcompoundmicroscope

The most familiar type of microscope is the optical, or light, microscope, in which glass lenses are used to form the image. Optical microscopes can be simple, consisting of a single lens, or compound, consisting of several optical components in line. The hand magnifying glass can magnify about 3 to 20×. Single-lensed simple microscopes can magnify up to 300×—and are capable of revealing bacteria—while compound microscopes can magnify up to 2,000×. A simple microscope can resolve below 1 micrometre (μm; one millionth of a metre); a compound microscope can resolve down to about 0.2 μm.

The word “microscope” comes from the Latin “microscopium,” which is derived from the Greek words “mikros,” meaning “small,” and “skopein,” meaning “to look at.”

Images of interest can be captured by photography through a microscope, a technique known as photomicrography. From the 19th century this was done with film, but digital imaging is now extensively used instead. Some digital microscopes have dispensed with an eyepiece and provide images directly on the computer screen. This has given rise to a new series of low-cost digital microscopes with a wide range of imaging possibilities, including time-lapse micrography, which has brought previously complex and costly tasks within reach of the young or amateur microscopist.

A microscope is an instrument that makes an enlarged image of a small object, thus revealing details too small to be seen by the unaided eye. The most familiar kind of microscope is the optical microscope, which uses visible light focused through lenses.

Principle of microscopediagram

Other types of microscopes use the wave nature of various physical processes. The most important is the electron microscope, which uses a beam of electrons in its image formation. The transmission electron microscope (TEM) has magnifying powers of more than 1,000,000×. TEMs form images of thin specimens, typically sections, in a near vacuum. A scanning electron microscope (SEM), which creates a reflected image of relief in a contoured specimen, usually has a lower resolution than a TEM but can show solid surfaces in a way that the conventional electron microscope cannot. There are also microscopes that use lasers, sound, or X-rays. The scanning tunneling microscope (STM), which can create images of atoms, and the environmental scanning electron microscope (ESEM), which generates images using electrons of specimens in a gaseous environment, use other physical effects that further extend the types of objects that can be examined.

electric polarization, slight relative shift of positive and negative electric charge in opposite directions within an insulator, or dielectric, induced by an external electric field. Polarization occurs when an electric field distorts the negative cloud of electrons around positive atomic nuclei in a direction opposite the field. This slight separation of charge makes one side of the atom somewhat positive and the opposite side somewhat negative. In some materials whose molecules are permanently polarized by chemical forces, such as water molecules, some of the polarization is caused by molecules rotating into the same alignment under the influence of the electric field. One of the measures of polarization is electric dipole moment, which equals the distance between the slightly shifted centres of positive and negative charge multiplied by the amount of one of the charges. Polarization P in its quantitative meaning is the amount of dipole moment p per unit volume V of a polarized material, P = p/V.