Translations of Encyclopedia about Physics

Optics

The word optics is derived from the Greek word of optiké, which means that which concerns vision. Optics studies light, which is that spectrum of electromagnetic waves which are visible to the human eye and whose wave length varies between 400 and 800 nm. Ultraviolet and infrared radiation, whose wave lengths are on the edge of the visible spectrum, are also studied under the subject of optics.

Physics studies light from three points of view, for which reason there are three categories: optic waves, which studies the wave characteristics of radiation; geometric optics, which studies the laws of the speed of linear radiation; and quantum optics, which examines the elementary characteristics of radiation. Geometric optics is based on the assumption that light travels in a straight line, definable using geometric methods. Wave optics perceives light radiation in terms of waves, where quantum physics looks at how light is made of a flow of small particles named corpuscles, as such adopting a quantum character.

During the 17^th century and based on knowledge gained in geometric optics, the first telescopes and microscopes were created. This is when the first concepts and theories of the nature of light were born and developed. Compared to this, optical instruments, such as glasses, were constructed long beforehand but, due to the imperfection of lenses at that time, telescopes could not be used effectively.

The second half of the nineteenth century brought the discovery that light travels along electromagnetic waves. Besides this, it brought the first atomic interpretation of optical phenomena, interpreted based on electron theory. However, optical development continued in a stormy fashion. A recent discovery has been the laser.

The word laser is derived from the string of words: light amplification by stimulated emission of radiation. The basis of a laser is the forced emission of electromagnetic radiation. Laser media with an activated energy state are, with the help of stimulated emissions, capable of amplifying electromagnetic radiation. The optical pump is made of atoms which are "pumped" up to a higher energy level until their light rays are strong enough to invoke a certain reaction under certain conditions.

Lasers are now used in many areas, such as in medicine, electronics, and measurement equipment for measuring extremely large or small distances. The advantage of lasers lies in the fact that a narrow band of light rays can be focused on a small area, which, for example, is useful for removing tissue infected with cancer cells without damaging surrounding tissue.

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