“light”的概念、定义、翻译、参考文献-科学参考

light

Physics

The form of electromagnetic radiation to which the human eye is sensitive and on which our visual awareness of the universe and its contents relies (see colour).

The finite velocity of light was suspected by many early experimenters in optics, but it was not established until 1676 when Ole Røemer (1644–1710) measured it. Sir Isaac Newton investigated the optical spectrum and used existing knowledge to establish a primarily corpuscular theory of light, in which it was regarded as a stream of particles that set up disturbances in the ‘aether’ of space. His successors adopted the corpuscles but ignored the wavelike disturbances until Thomas Young rediscovered the interference of light in 1801 and showed that a wave theory was essential to interpret this type of phenomenon. This view was accepted for most of the 19th century and it enabled James Clerk Maxwell to show that light forms part of the electromagnetic spectrum. He believed that waves of electromagnetic radiation required a special medium to travel through, and revived the name ‘luminiferous ether’ for such a medium. The Michelson–Morley experiment in 1887 showed that, if the medium existed, it could not be detected; it is now generally accepted that the ether is an unnecessary hypothesis. In 1905 Albert Einstein showed that the photoelectric effect could only be explained on the assumption that light consists of a stream of discrete photons of electromagnetic energy. This renewed conflict between the corpuscular and wave theories has gradually been resolved by the evolution of the quantum theory and wave mechanics. While it is not easy to construct a model that has both wave and particle characteristics, it is accepted, according to the theory of complementarity proposed by Niels Bohr, that in some experiments light will appear wavelike, while in others it will appear to be corpuscular. During the course of the evolution of wave mechanics it has also become evident that electrons and other elementary particles have dual wave and particle properties.

Mathematics

In mechanics, an object such as a string or a rod is said to be light if its weight may be considered negligible compared with that of other objects involved.

Astronomy

Electromagnetic radiation that can be seen by the human eye. It lies between the ultraviolet and infrared regions of the electromagnetic spectrum. Different wavelengths of light appear as different colours. Visible radiation ranges from wavelengths of about 750 nm at the red (long-wavelength) end to around 380 nm at the violet (short-wavelength) end.

Space Exploration

The electromagnetic waves in the visible range, having a wavelength between about 400 nanometres in the extreme violet and about 770 nanometres in the extreme red. Light is considered to exhibit both particle and wave properties, and the fundamental particle, or quantum, of light is called the photon. The speed of light (and of all electromagnetic radiation) in a vacuum is 299 792.5 km/s and is a universal constant denoted by c.

Philosophy

Although in physics light is well understood as electromagnetic energy of a very specific wavelength (between 390 and 740 nanometers: a nanometer is 10⁻⁹ metre), the fact that this is just the energy that illuminates the world for us is evidently contingent upon the nature of our senses, and upon the adaptations they have made to the environment. Light can thus come to inherit the problems of secondary qualities (see primary/secondary qualities), and just as the fact that trees are green can seem due to our design as much as to non-human nature, so the fact that it is light or dark may seem disturbingly anthropocentric or subjective. Descartes put the problem by asking ‘could nature not also have established some sign, which would make us have the sensation of light, even if the sign contained nothing in itself which is similar to this sensation?’ (Le Monde). Light has been associated with the original primal creative principle in many religious and philosophical traditions, including Zoroastrianism and Neoplatonism.

单词	light
释义	light Physics The form of electromagnetic radiation to which the human eye is sensitive and on which our visual awareness of the universe and its contents relies (see colour). The finite velocity of light was suspected by many early experimenters in optics, but it was not established until 1676 when Ole Røemer (1644–1710) measured it. Sir Isaac Newton investigated the optical spectrum and used existing knowledge to establish a primarily corpuscular theory of light, in which it was regarded as a stream of particles that set up disturbances in the ‘aether’ of space. His successors adopted the corpuscles but ignored the wavelike disturbances until Thomas Young rediscovered the interference of light in 1801 and showed that a wave theory was essential to interpret this type of phenomenon. This view was accepted for most of the 19th century and it enabled James Clerk Maxwell to show that light forms part of the electromagnetic spectrum. He believed that waves of electromagnetic radiation required a special medium to travel through, and revived the name ‘luminiferous ether’ for such a medium. The Michelson–Morley experiment in 1887 showed that, if the medium existed, it could not be detected; it is now generally accepted that the ether is an unnecessary hypothesis. In 1905 Albert Einstein showed that the photoelectric effect could only be explained on the assumption that light consists of a stream of discrete photons of electromagnetic energy. This renewed conflict between the corpuscular and wave theories has gradually been resolved by the evolution of the quantum theory and wave mechanics. While it is not easy to construct a model that has both wave and particle characteristics, it is accepted, according to the theory of complementarity proposed by Niels Bohr, that in some experiments light will appear wavelike, while in others it will appear to be corpuscular. During the course of the evolution of wave mechanics it has also become evident that electrons and other elementary particles have dual wave and particle properties. Mathematics In mechanics, an object such as a string or a rod is said to be light if its weight may be considered negligible compared with that of other objects involved. Astronomy Electromagnetic radiation that can be seen by the human eye. It lies between the ultraviolet and infrared regions of the electromagnetic spectrum. Different wavelengths of light appear as different colours. Visible radiation ranges from wavelengths of about 750 nm at the red (long-wavelength) end to around 380 nm at the violet (short-wavelength) end. Space Exploration The electromagnetic waves in the visible range, having a wavelength between about 400 nanometres in the extreme violet and about 770 nanometres in the extreme red. Light is considered to exhibit both particle and wave properties, and the fundamental particle, or quantum, of light is called the photon. The speed of light (and of all electromagnetic radiation) in a vacuum is 299 792.5 km/s and is a universal constant denoted by c. Philosophy Although in physics light is well understood as electromagnetic energy of a very specific wavelength (between 390 and 740 nanometers: a nanometer is 10⁻⁹ metre), the fact that this is just the energy that illuminates the world for us is evidently contingent upon the nature of our senses, and upon the adaptations they have made to the environment. Light can thus come to inherit the problems of secondary qualities (see primary/secondary qualities), and just as the fact that trees are green can seem due to our design as much as to non-human nature, so the fact that it is light or dark may seem disturbingly anthropocentric or subjective. Descartes put the problem by asking ‘could nature not also have established some sign, which would make us have the sensation of light, even if the sign contained nothing in itself which is similar to this sensation?’ (Le Monde). Light has been associated with the original primal creative principle in many religious and philosophical traditions, including Zoroastrianism and Neoplatonism.
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