Light moves in a straight line, creating shadows when the path of light is blocked. More solid things will have a darker shadow, things that are more clear have a.
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The raindrop acts like a prism and refracts the light until we can see the colors of the spectrum. Light and color are forms of analog information. However, electronic cameras and computer displays work with digital information. So, electronic cameras or document scanners make a digital version of a color image by separating out the full color image into separate red , green , and blue images. Later, a digital display uses pixels of just those three colors. Computer screens use only these three colors in different brightness levels.
The brain combines them to see all of the other colors in the image. People think of objects as having color. Scientist explain this because the molecules that make up the object absorb certain light waves, leaving the other light waves to bounce off. The human eye sees the wavelengths of all of the light that was not absorbed, and the combination of those leaves the brain with the impression of a color. From Wikipedia, the free encyclopedia. For all parts of the electromagnetic spectrum that can be seen by the eye, see Visible spectrum.
By the International Lighting Vocabulary , the definition of light is: Wonders of the Universe. Light as a Cosmic Time Machine". Retrieved 13 August Light speed reduction to 17 metres per second in an ultracold atomic gas. Retrieved from " https: Pages with citations using unnamed parameters. Views Read Change Change source View history.
In other projects Wikimedia Commons. Through the sense of sight, light is a primary tool for perceiving the world and communicating within it. Light from the Sun warms the Earth , drives global weather patterns, and initiates the life-sustaining process of photosynthesis. Indeed, light provides a window on the universe, from cosmological to atomic scales.
Almost all of the information about the rest of the universe reaches Earth in the form of electromagnetic radiation.
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By interpreting that radiation, astronomers can glimpse the earliest epochs of the universe, measure the general expansion of the universe, and determine the chemical composition of stars and the interstellar medium. Just as the invention of the telescope dramatically broadened exploration of the universe, so too the invention of the microscope opened the intricate world of the cell. The analysis of the frequencies of light emitted and absorbed by atoms was a principal impetus for the development of quantum mechanics. Atomic and molecular spectroscopies continue to be primary tools for probing the structure of matter, providing ultrasensitive tests of atomic and molecular models and contributing to studies of fundamental photochemical reactions.
Light transmits spatial and temporal information. This property forms the basis of the fields of optics and optical communications and a myriad of related technologies, both mature and emerging. Technological applications based on the manipulations of light include lasers , holography , and fibre-optic telecommunications systems. In most everyday circumstances, the properties of light can be derived from the theory of classical electromagnetism , in which light is described as coupled electric and magnetic fields propagating through space as a traveling wave.
However, this wave theory, developed in the midth century, is not sufficient to explain the properties of light at very low intensities. At that level a quantum theory is needed to explain the characteristics of light and to explain the interactions of light with atoms and molecules. In its simplest form, quantum theory describes light as consisting of discrete packets of energy , called photons. However, neither a classical wave model nor a classical particle model correctly describes light; light has a dual nature that is revealed only in quantum mechanics. This surprising wave-particle duality is shared by all of the primary constituents of nature e.
Since the midth century, a more comprehensive theory of light, known as quantum electrodynamics QED , has been regarded by physicists as complete. QED combines the ideas of classical electromagnetism, quantum mechanics, and the special theory of relativity. This article focuses on the physical characteristics of light and the theoretical models that describe the nature of light. Its major themes include introductions to the fundamentals of geometrical optics, classical electromagnetic waves and the interference effects associated with those waves, and the foundational ideas of the quantum theory of light.
More detailed and technical presentations of these topics can be found in the articles optics , electromagnetic radiation , quantum mechanics , and quantum electrodynamics. Visible light is the most familiar form of electromagnetic radiation and makes up that portion of the spectrum to which the eye is sensitive.
This span is very narrow; the frequencies of violet light are only about twice those of red. The corresponding wavelengths extend from….
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While there is clear evidence that simple optical instruments such as plane and curved mirrors and convex lenses were used by a number of early civilizations, ancient Greek philosophers are generally credited with the first formal speculations about the nature of light. The conceptual hurdle of distinguishing the human perception of visual effects from the physical nature of light hampered the development of theories of light. To explain the origin of colors, Robert Hooke developed a "pulse theory" and compared the spreading of light to that of waves in water in his work Micrographia "Observation IX".
In Hooke suggested that light's vibrations could be perpendicular to the direction of propagation. Christiaan Huygens worked out a mathematical wave theory of light in , and published it in his Treatise on light in He proposed that light was emitted in all directions as a series of waves in a medium called the Luminiferous ether.
As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium. The wave theory predicted that light waves could interfere with each other like sound waves as noted around by Thomas Young. Young showed by means of a diffraction experiment that light behaved as waves. He also proposed that different colours were caused by different wavelengths of light, and explained colour vision in terms of three-coloured receptors in the eye. Another supporter of the wave theory was Leonhard Euler. He argued in Nova theoria lucis et colorum that diffraction could more easily be explained by a wave theory.
The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. The existence of the hypothetical substance luminiferous aether proposed by Huygens in was cast into strong doubt in the late nineteenth century by the Michelson—Morley experiment.
Light - Wikipedia
Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied the opposite. At that time, the speed of light could not be measured accurately enough to decide which theory was correct. In , Michael Faraday discovered that the plane of polarisation of linearly polarised light is rotated when the light rays travel along the magnetic field direction in the presence of a transparent dielectric , an effect now known as Faraday rotation. In he speculated that light might be some form of disturbance propagating along magnetic field lines.
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Faraday's work inspired James Clerk Maxwell to study electromagnetic radiation and light. Maxwell discovered that self-propagating electromagnetic waves would travel through space at a constant speed, which happened to be equal to the previously measured speed of light. From this, Maxwell concluded that light was a form of electromagnetic radiation: In , he published A Treatise on Electricity and Magnetism , which contained a full mathematical description of the behaviour of electric and magnetic fields, still known as Maxwell's equations.
Soon after, Heinrich Hertz confirmed Maxwell's theory experimentally by generating and detecting radio waves in the laboratory, and demonstrating that these waves behaved exactly like visible light, exhibiting properties such as reflection, refraction, diffraction, and interference. Maxwell's theory and Hertz's experiments led directly to the development of modern radio, radar, television, electromagnetic imaging, and wireless communications.
In the quantum theory, photons are seen as wave packets of the waves described in the classical theory of Maxwell. The quantum theory was needed to explain effects even with visual light that Maxwell's classical theory could not such as spectral lines. In Max Planck , attempting to explain black body radiation suggested that although light was a wave, these waves could gain or lose energy only in finite amounts related to their frequency.
Planck called these "lumps" of light energy "quanta" from a Latin word for "how much". In , Albert Einstein used the idea of light quanta to explain the photoelectric effect , and suggested that these light quanta had a "real" existence. In Arthur Holly Compton showed that the wavelength shift seen when low intensity X-rays scattered from electrons so called Compton scattering could be explained by a particle-theory of X-rays, but not a wave theory.
In Gilbert N. Lewis named these light quanta particles photons. Eventually the modern theory of quantum mechanics came to picture light as in some sense both a particle and a wave, and in another sense , as a phenomenon which is neither a particle nor a wave which actually are macroscopic phenomena, such as baseballs or ocean waves.
Instead, modern physics sees light as something that can be described sometimes with mathematics appropriate to one type of macroscopic metaphor particles , and sometimes another macroscopic metaphor water waves , but is actually something that cannot be fully imagined. As in the case for radio waves and the X-rays involved in Compton scattering, physicists have noted that electromagnetic radiation tends to behave more like a classical wave at lower frequencies, but more like a classical particle at higher frequencies, but never completely loses all qualities of one or the other.
Visible light, which occupies a middle ground in frequency, can easily be shown in experiments to be describable using either a wave or particle model, or sometimes both. In February , scientists reported, for the first time, the discovery of a new form of light, which may involve polaritons , that could be useful in the development of quantum computers. From Wikipedia, the free encyclopedia. For light that cannot be seen with human eye, see Electromagnetic radiation. For other uses, see Light disambiguation and Visible light disambiguation.
For the solar energy developer named Lightsource, see Lightsource Renewable Energy. List of light sources. Photometry optics and Radiometry. SI radiometry units v t e. SI photometry quantities v t e.
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May Learn how and when to remove this template message. Corpuscular theory of light. Physics portal Science portal. By the International Lighting Vocabulary , the definition of light is: Textbook of Practical Physiology 1st ed. Retrieved 11 October The human eye has the ability to respond to all the wavelengths of light from — nm.
This is called the visible part of the spectrum. The Natural Laws of the Universe: Introduction to Optics and Lasers in Engineering. Retrieved 20 October A Physical Approach to Astronomical Observations. Handbook of Pharmaceutical Analysis. A Textbook of Organic Chemistry. Journal of the Optical Society of America. The foveal sensitivity to several near-infrared laser wavelengths was measured.
It was found that the eye could respond to radiation at wavelengths at least as far as nm. A continuous nm laser source appeared red, but a nm pulsed laser source appeared green, which suggests the presence of second harmonic generation in the retina. Color and Light in Nature 2nd ed. Retrieved 12 October Fundamentals Of Ecology 3E.
Retrieved 18 October Normally the human eye responds to light rays from to nm. This can be extended to a range of to 1, nm under artificial conditions. Retrieved 12 March Researchers now able to stop, restart light". Archived from the original on 28 October On the development of our views concerning the nature and constitution of radiation. The Collected Papers of Albert Einstein, vol.
Fundamentals of Optical Engineering. Ancient Greece to Maxwell". Ptolemy's Theory of Visual Perception: Enlightenment and Electrodynamics , Cambridge University Press, , p. Theoretical Concepts in Physics. Retrieved 17 February Explicit use of et al. Color model additive subtractive Color mixing Primary color Secondary color Tertiary color intermediate Quaternary color Quinary color Aggressive color warm Receding color cool Pastel colors Color gradient. Color tool Monochromatic colors Complementary colors Analogous colors Achromatic colors Neutral Polychromatic colors Impossible colors Light-on-dark Tinctures in heraldry.
Chromaticity diagram Color solid Color wheel Color triangle Color analysis art Color realism art style. Linguistic relativity and the color naming debate Blue—green distinction in language Color history Color in Chinese culture Traditional colors of Japan Human skin color. Hue Dichromatism Colorfulness chroma and saturation Tints and shades Lightness tone and value Grayscale. A—F List of colors: G—M List of colors: