Copyright © Philip M. Parker, INSEAD. Terms of Use.
Definition: Light |
LightAdjective1. Of comparatively little physical weight or density; "a light load"; "magnesium is a light metal--having a specific gravity of 1.74 at 20 degrees C". 2. (used of color) having a relatively small amount of coloring agent; "light blue"; "light colors such as pastels"; "a light-colored powder". 3. Of the military or industry; using (or being) relatively small or light arms or equipment; "light infantry"; "light cavalry"; "light industry"; "light weapons". 4. Not great in degree or quantity or number; "a light sentence"; "a light accent"; "casualties were light"; "light snow was falling"; "light misty rain"; "light smoke from the chimney". 5. Psychologically light; especially free from sadness or troubles; "a light heart". 6. Characterized by or emitting light; "a room that is light when the shutters are open"; "the inside of the house was airy and light". 7. Used of vowels or syllables; pronounced with little or no stress; "a syllable that ends in a short vowel is a light syllable"; "a weak stress on the second syllable". 8. Easily assimilated in the alimentary canal; not rich or heavily seasoned; "a light diet". 9. (used of soil) loose and large-grained in consistency; "light sandy soil". 10. : (of sound or color) free from anything that dulls or dims; "efforts to obtain a clean bass in orchestral recordings"; "clear laughter like a waterfall"; "clear reds and blues"; "a light lilting voice like a silver bell". 11. : moving easily and quickly; nimble; "the dancer was light and graceful"; "a lightsome buoyant step"; "walked with a light tripping step". 12. : demanding little effort; not burdensome; "light housework"; "light exercise". 13. : of little intensity or power or force; "the light touch of her fingers"; "a light breeze". 14. : (physics, chemistry) not having atomic weight greater than average; "light water is ordinary water". 15. : weak and likely to lose consciousness; "suddenly felt faint from the pain"; "was sick and faint from hunger"; "felt light in the head"; "a swooning fit"; "light-headed with wine"; "light-headed from lack of sleep". 16. : very thin and insubstantial; "thin paper"; "flimsy voile"; "light summer dresses". 17. : marked by temperance in indulgence; "abstemious meals"; "a light eater"; "a light smoker"; "ate a light supper". 18. : less than the correct or legal or full amount often deliberately so; "a light pound"; "a scant cup of sugar"; "regularly gives short weight". 19. : having little importance; "losing his job was no light matter". 20. : intended primarily as entertainment; not serious or profound; "light verse"; "a light comedy". 21. : silly or trivial; "idle pleasure"; "light banter"; "light idle chatter". 22. : having a spongy or flaky texture; well-leavened; "light pastries". 23. : designed for ease of movement or to carry little weight; "light aircraft"; "a light truck". 24. : having relatively few calories; "diet cola"; "light (or lite) beer"; "lite (or light) mayonnaise"; "a low-cal diet". 25. : (of sleep) easily disturbed; "in a light doze"; "a light sleeper"; "a restless wakeful night". 26. : casual and unrestrained in sexual behavior; "her easy virtue"; "he was told to avoid loose (or light) women"; "wanton behavior". Adverb1. With few burdens; "experienced travellers travel light". Noun1. (physics) electromagnetic radiation that can produce a visual sensation; "the light was filtered through a soft glass window". 2. Any device serving as a source of illumination; "he stopped the car and turned off the lights". 3. A particular perspective or aspect of a situation; "although he saw it in a different light, he still did not understand". 4. The quality of being luminous; emitting or reflecting light; "its luminosity is measured relative to that of our sun". 5. An illuminated area; "he stepped into the light". 6. A condition of spiritual awareness; divine illumination; "follow God's light". 7. The visual effect of illumination on objects or scenes as created in pictures; "he could paint the lightest light and the darkest dark". 8. A person regarded very fondly; "the light of my life". 9. Mental understanding as an enlightening experience; "he finally saw the light"; "can you shed light on this problem?". 10. : having abundant light or illumination: "they played as long as it was light" or "as long as the lighting was good". 11. : public awareness; "it brought the scandal to light". 12. : brightness and animation of countenance; "he had a sparkle in his eye". 13. : a divine presence believed by Quakers to enlighten and guide the soul. 14. : a visual warning signal; "they saw the light of the beacon"; "there was a light at every corner". 15. : a device for lighting or igniting fuel or charges or fires; "do you have a light?". Verb1. Make lighter or brighter; "This lamp lightens the room a bit". 2. Begin to smoke; "After the meal, some of the diners lit up". 3. To come to rest, settle: "Misfortune lighted upon him.". 4. Cause to start burning; subject to fire or great heat; "Great heat can ignite almost any dry matter."; "Light a cigarette.". 5. Fall to somebody by assignment or lot: "The task fell to me"; "It fell to me to notify the parents of the victims". 6. Get off (a horse). Source: WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. |
Date "light" was first used in popular English literature: sometime before 1010. (references) |
| Domain | Definition |
Computing | LIGHT LIfecycle Global HyperText. A project in the CERN ECP/TP group whereby documents resulting from the software life cycle are available as hypertext. (1995-02-03). Source: The Free On-line Dictionary of Computing. |
Aerospace | Visible radiation (about 0.4 to 0.7 micron in wavelength) considered in terms of its luminous efficiency, i.e., evaluated in proportion to its ability to stimulate the sense of sight. (references) |
Bible | Light the offspring of the divine command (Gen. 1:3). "All the more joyous emotions of the mind, all the pleasing sensations of the frame, all the happy hours of domestic intercourse were habitually described among the Hebrews under imagery derived from light" (1 Kings 11:36; Isa. 58:8; Esther 8:16; Ps. 97:11). Light came also naturally to typify true religion and the felicity it imparts (Ps. 119:105; Isa. 8:20; Matt. 4:16, etc.), and the glorious inheritance of the redeemed (Col. 1:12; Rev. 21:23-25). God is said to dwell in light inaccessible (1 Tim. 6:16). It frequently signifies instruction (Matt. 5:16; John 5:35). In its highest sense it is applied to Christ as the "Sun of righteousness" (Mal. 4:2; Luke 2:32; John 1:7-9). God is styled "the Father of lights" (James 1:17). It is used of angels (2 Cor. 11:14), and of John the Baptist, who was a "burning and a shining light" (John 5:35), and of all true disciples, who are styled "the light of the world" (Matt. 5:14). Source: Easton's 1897 Bible Dictionary. |
Building & Civil Engineering | The portion of a window which is confined by the casement or the jambs, sill and window frame head and/or the mullion. Source: European Union. (references) |
Dream Interpretation | If you dream of light, success will attend you. To dream of weird light, or if the light goes out, you will be disagreeably surprised by some undertaking resulting in nothing. To see a dim light, indicates partial success. Source: Ten Thousand Dreams Interpreted .... |
Food & Agriculture | Term applied to a wine low in alcohol, extract and colour but which may be well balanced. Source: European Union. (references) |
Literature | Light Life. Othello says, "Put out the light and then put out the light." In May, 1886, Abraham Harper, a market-gardener, of Oxford, hit his wife in the face, and threatened to "put her light out," for which he was fined 5s. and costs. (Truth, May 20th, 1886.) Light Graces, holiness. Called "the candle of the Lord," the "lamp of God," as, "The spirit of man is the lamp of the Lord." (Prov. xx. 27.) "Let your light so shine before men that they may see your good works."- Matt. v. 16. To stand in one's own light. To act in such a way as to hinder advancement. "He stands in his own light through nervous fear."- The Leisure Hour, 1886. Source: Brewer's Dictionary. |
Medicine | The attribute of all the perceptions or sensations which are peculiar to the organ of vision and which are produced through the agency of that organ. Source: European Union. (references) |
| Radiation capable of stimulating the organ of vision. Source: European Union. (references) | |
Multilingual Slang | Hungarian (pilács). (references) |
Physics | The electromagnetic radiation in a band of frequencies that can be received by the human eye. Source: European Union. (references) |
| Any radiation capable of causing a visual sensation directly. Source: European Union. (references) | |
| Electromagnetic radiation that is visible to the human eye. (references) | |
Post & Telecom | A source of light used as a signal: as. . . a ship's blinker light (called the flagship on the light to announce she was reporting on duty). Source: European Union. (references) |
Science | 1. Form of radiant energy that acts upon the retina of the eye, optic nerve, etc., making sight possible. This energy is transmitted at a velocity of about 186,000 miles per second by wavelike or vibrational motion. 2. A form of radiant energy similar to this, but not acting on the normal retina, such as ultraviolet and infrared radiation. Interplay between light rays and the atmosphere cause us to see the sky as blue, and can result in such phenomena as glows, halos, arcs, flashes, and streamers. (references) |
Solar | Usually the visual portion of the electromagnetic spectrum between infrared (about 8000 Angstroms or 800 nanometers(nm)) and ultraviolet (about 4,000 Angstroms or 400 nm); however, the term is sometimes used as a synonym for all electromagnetic radiation. (references) |
Space | Electromagnetic radiation in the neighborhood of 1 nanometer wavelength. (references) |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
Cherenkov radiation is electromagnetic radiation emitted when a charged particle passes through an insulator at a velocity greater than the speed of light in that material. The characteristic "blue glow" of nuclear reactors is due to Cherenkov radiation. It is named for Pavel Alekseyevich Cherenkov, the 1958 Nobel Prize winner who was the first to rigorously characterize it.
Physical Origin
While relativity holds that the speed of light in a vacuum is a universal constant (c), the speed of light in a material may be significantly less than c. For example, the speed of light in water is only 0.75×c. Matter can be accelerated beyond this speed during nuclear reactions and in particle accelerators. Cherenkov radiation results when a charged particle, most commonly an electron, exceeds the speed of light in a dielectric medium through which it passes.
As a charged particle travels, it disrupts the local electromagnetic field in its medium. Electrons in the atoms of the medium will be displaced and polarized by the passing EM field of a charged particle. Photons are emitted as an insulator's electrons restores themselves to equilibrium after the disruption has passed. (In a conductor, the EM disruption can be restored without emitting a photon.) In normal circumstances, these photons destructively interfere with each other and no radiation is detected. However, when the disruption travels faster than the photons themselves travel, the photons constructively interfere and intensify the observed radiation.
A common analogy is the sonic boom of a supersonic aircraft or bullet. The sound waves generated by the supersonic body do not move fast enough to get out of the way of the body itself. Hence, the waves "stack up" and form a shock front. Similarly, a speed boat generates a large bow shock because it travels faster than waves can move on the surface of the water.
In the same way, a superluminal charged particle generates a photonic shockwave as it travels through an insulator.
Characteristics
Intuitively, the overall intensity of Cherenkov radiation is proportional to the velocity of the inciting charged particle and to the number of such particles. Unlike fluorescence or emission spectra that have characteristic spectral peaks, Cherenkov radiation is continuous. The relative intensity of one frequency is proportional to the frequency. That is, higher frequencies (shorter wavelengths) are more intense in Cherenkov radiation. This is why visible Cherenkov radiation is observed to be brilliant blue. In fact, most Cherenkov radiation is in the ultraviolet spectrum - it is only with sufficiently accelerated charges that it even becomes visible.
As in sonic booms and bow shocks, the angle of the shock cone is inversely related to the velocity of the disruption. Hence, observed angles of incidence can be used to compute the direction and speed of a Cherenkov radiation producing charge.
Uses
Cherenkov radiation is used to detect high-energy charged particles. In nuclear reactors, the intensity of Cherenkov radiation is related to the frequency of the fission events that produce high-energy electrons, and hence is a measure of the intensity of the reaction. Cherenkov radiation is also used to characterize the remaining radioactivity of spent fuel rods.
When a high-energy cosmic ray impacts the Earth's atmosphere, it can produce an electron-positron pair with enormous velocities. The Cherenkov radiation from these charged particles is used to determine the source and intensity of the cosmic rays. Similar methods are used in very large neutrino detectors, such as the Super-Kamiokande
The Cherenkov effect is used as a visual cue in Hollywood movies to announce radioactive materials - no doubt the reason for the general public awareness of the effect.
Notes
- Cerenkov effect image provided by and © the Nuclear Engineering Department of the University of Missouri-Rolla; used by kind permission of Dr. Akira T. Tokuhiro. See http://www.nuc.umr.edu/reactor/reactor.html for the original context.
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Cherenkov effect."
(From Wikipedia, the free Encyclopedia)
Nature of Light
The term "light" (light beam or light ray) refers to the portion of the electromagnetic spectrum visible to the human eye, but can also include other forms of electromagnetic radiation. The three basic dimensions of light (and of all electromagnetic radiation) are brilliance (or amplitude), color (or frequency), and polarization (or angle of vibration). Due to wave-particle duality, light simultaneously exhibits properties of both waves and particles.
Theories About Light
- Particle Thoery
- First proposed by Isaac Newton in the seventeenth century
- Argues that light is made up of tiny particles of matter (corpuscles)
- <Discounted>
- Corpuscles are emitted in all directions
- <Discounted>
- Supports the fact that light is reflected
- Argues that light speeds up upon entering a denser medium because gravitational pull is greater
- <Discounted>
- Greatly discounted by wave theory
- Wave (or Ray) Theory
- First proposed by Christian Huygens in the seventeenth century
- Argues that light is emitted as a series of waves only
- <Discounted>
- Waves are emitted in all directions
- Waves not affected by gravity, so they slow down upon entering a denser medium
- Greatly discounted the corpuscular theory
- Can interfere with each other like sound waves (noted in eighteenth century by Thomas Young)
- Waves can be polarized
- Assumes that light needs a medium for transmission like sound
- <Discounted>
- Electromagnetic Theory
- Argues that light waves are electromagnetic and do not need a medium
- Proposed by James Clerk Maxwell at the end of the nineteenth century
- Shows that visible light is part of the electromagnetic spectrum
- Quantum (or Wave-particle duality) Theory
- Combines previous three theories
- Pioneered at end of the nineteenth century
- Max Planck proposed that light waves are made of packets of energy known as quanta or photons in 1900
- Light behaves as both particles and waves
Visible Light Wavelengths
Visible light is that portion of the spectrum between the wavelengths of about 400 nanometers (abbreviated nm) and 800 nm (in air). Light can also be characterized by its frequency. The frequency and wavelength of light obey the relation
The Speed of Light
Speed of Light Formula
where λ is the wavelength, f is the frequency, v is the speed of the light. If the light is travelling in a vacuum, then v = c, thus
- ,
where c is the speed of light. We can express v as
- ,
where n is a constant (the refractive index) which is a property of the material through which the light is passing.
Change to the Speed of Light
All light propagates at a finite speed. Even moving observers always measure the same value of c, the speed of light in vacuum, as c = 299,792,458 metres per second; however, when light passes through a transparent substance such as air, water or glass, its speed is reduced, and it suffers refraction. Thus, n=1 in a vacuum and n>1 in matter. It is a violation of the technical terminology of physics to speak of the "velocity of light;" velocity is reserved for a different use.
History of the Speed of Light
The speed of light has been measured many times, by many physicists. The best early measurement is Olaus Roemer's (a Danish physicist), in 1676. He had developed a method for measuring light. He observed and noted the motions of Jupiter and one of its moonss with a telescope. It was possible to time the revolution of the moon because it was eclipsed by Jupiter at regular intervals. Roemer discovered that the moon revolved around Jupiter once every 42-1/2 hours when Earth was closest to Jupiter. The problem was that when Earth and Jupiter were not as close, the moon's revolution seemed to be more. It was clear that light took longer to reach Earth when it was farther away from Jupiter. The speed of light was calculated by analyzing the distance between the two planets at various times. Roemer reached a speed of 227,000 kilometers per second (approximately 141,050 miles per second).
Albert A. Michelson improved on Roemer's work in 1926. He used rotating mirrors to measure the time it took light to make a round trip from Mt. Wilson to Mt. San Antonio in California. The precise measurements yielded a speed of 186,285 miles/second (299,796 kilometers/second). In daily use, the figures are rounded off to 186,000 mi/sec and 300,000 km/sec.
Optics
The study of light and the interaction of light and matter is termed optics. The observation and study of optical phenomena such as rainbows offers many clues as to the nature of light as well as much enjoyment.
Color and Wavelengths
The different wavelengths are interpreted by the human brain as colors, ranging from red at the longest wavelengths (lowest frequencies) to violet at the shortest wavelengths (highest frequencies). The intervening frequencies are seen as orange, yellow, green, blue, and, conventionally, indigo. The frequencies of the spectrum immediately outside the range the human eye is able to perceive are called ultraviolet (UV) at the high frequency end and infrared (IR) at the low. Though humans cannot see IR, we do perceive it by receptors in the skin as heat. Cameras that can pick up IR and convert it to visible light are called night-vision cameras. UV radiation is not perceived by humans at all except in a very delayed fashion, as overexposure of the skin to UV light causes sunburn, or skin cancer. Some animals, such as bees, can see UV radiation while others, such as pit viper snakes, can see IR using pits in their heads.
Measurement of Light
The following quantities and units are used to measure light.
- brightness (or temperature)
- illuminance or illumination (SI unit: lux)
- luminous flux (SI unit: lumen)
- luminous intensity (SI unit: candela)
Light Sources
- thermal radiation (black body radiation)
- incandescent light bulbs
- sunlight
- glowing solid particles in flames (see fire)
- atomic spectral emission (emission lines can either be stimulated or spontaneous)
- laser and maser (stimulated emission)
- light emitting diodes
- gas discharge lamps (neon signs, mercury lamps, etc)
- flames (light from the hot gas itself, see also above)
- acceleration of a free charged particle (usually an electron)
- cyclotron radiation
- Bremsstrahlung radiation
- Cherenkov radiation
- chemoluminescence
- fluorescence
- phosphorescence
- cathode ray tube
- bioluminescence
- sonoluminescence
- triboluminescence
- radioactive decay
- particle-antiparticle annihilation
Light Waves
A light wave
See also: Huygens' principle, Color temperature, Illumination, International Commission on Illumination, Wave-particle duality, Light pollution, photic sneeze reflex
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Light."
(From Wikipedia, the free Encyclopedia)
Overview
According to standard modern physical theory, light and all other electromagnetic radiation propagates (or moves) at a constant speed in vacuum, the speed of light. It is a physical constant and notated as (from the Latin celeritas, "speed"). Regardless of the reference frame of an observer or the velocity of the object emitting the light, every observer will obtain the same value for the speed of light upon measurement. No information can travel faster than without causing serious problems with causality that have not been observed.The value is precisely
or about thirty centimetres (12 inches) in a nanosecondsecond. This is not an empirical value -- in 1983 the metre was redefined to give c precisely this value, chosen to be approximately the same as the previous value. It gives a solution to the wave equation, and can be calculated from the permittivity of free space () and the permeability of free space (). In fact
- c = 2.997 924 58 × 108 metres per second,
Constant in all Reference Frames
It is important to realize that the speed of light is not a "speed limit" in the conventional sense. As a consequence of the theory of special relativity, all observers will measure the speed of light as being the same. An observer chasing a beam of light well measure it moving away from him at the same speed as a stationary observer. This leads to some unusual consequences for velocities.We are accustomed to the additive rule of velocities: if two cars approach each other, each travelling at a speed of 50 miles per hour, we expect that each car will perceive the other as approaching at a combined speed of miles per hour (to a very high degree of accuracy).
At velocities approaching or at the speed of light, however, it becomes clear from experimental results that this additive rule no longer applies. Two spaceships approaching each other, each travelling at 90% the speed of light relative to some third observer between them, do not perceive each other as approaching at 90 + 90 = 180% the speed of light; instead they each perceive the other as approaching at slightly less than 99.5% the speed of light.
This last result is given by the Einstein velocity addition formula:
where and are the speeds of the spaceships relative to the observer, and is the speed perceived by each spaceship.
Contrary to our usual intuitions, regardless of the speed at which one observer is moving relative to another observer, both will measure the speed of an incoming light beam as the same constant value, the speed of light.
Albert Einstein developed the theory of relativity by applying the (somewhat bizarre) consequences of the above to classical mechanics. Experimental confirmations of the theory of relativity directly and indirectly confirm that the velocity of light has a constant magnitude, independent of the motion of the observer.
Since the speed of light in vacuum is constant, it is convenient to measure both time and distance in terms of . Both the SI unit of length and SI unit of time have been defined in terms of wavelengths and cycles of light. In particular, a meter is defined as exactly c/299792458 * 1 second. This relies on the constancy of the velocity of light for all observers. Distances in physical experiment or astronomy are commonly measured in light seconds, light minutes, or light years.
Refraction
In passing through materials, light is slowed to less than , by the ratio called the refractive index of the material. The speed of light in air is only slightly less than . Denser media such as water and glass can slow light much more, to fractions such as 3/4 and 2/3 of . On the microscopic scale this is caused by continual absorption and re-emission of the photons that compose the light by the atoms or molecules through which it is passing.
"Faster-than-light" experiments
Recent experimental evidence shows that it is possible for the group velocity of light to exceed c. One experiment made the group velocity of laser beams travel for extremely short distances through caesium atoms at 300 times . However, it is not possible to use this technique to transfer information faster than ; the product of the group velocity and the velocity of information transfer is equal to the square of the normal speed of light in the material.Exceeding the group velocity of light in this manner is comparable to exceeding the speed of sound by arranging people in a distantly spaced line of people, and asking them all to shout "I'm here!", one after another with short intervals, each one timing it by looking at their own wristwatch so they don't have to wait until they hear the last person shouting.
The speed of light may also appear to be exceeded in some phenomena involving evanescent waves. Again, it is not possible that information is transmitted faster than .
See also: tachyon
"Slower-Than-Light" (i.e. slowing light) Experiments
In 1999, a team of scientists led by Lene Hau were able to slow the speed of a light beam to about 61 km/h. In 2001, they were able to momentarily stop a beam. See Bose-Einstein condensate for more information.History
Galileo Galilei as far as we know was the first person to suspect that light might have a finite speed and attempt to measure it-but people before Galileo probably thought of lights (i.e. stars, suns) as constants anyway. He wrote about his unsuccessful attempt using lanterns flashed from hill to hill outside Florence. The speed of light was first measured in 1676, some decades after Galileo's attempt, by Rømer, who was studying the motions of Jupiter's moonss. A plaque at the Observatory of Paris, where the Danish astronomer happened to be working, commemorates what was, in effect, the first measurement of a universal quantity made on this planet. Rømer published his result, which had an error of 10-25%, in Journal des Scavans.
It is a bizarre coincidence that the average speed of the earth in its orbit is very close to one ten-thousandth of this, actually within less than a percent. This gives a hint as to how Rømer measured light's speed. He was recording eclipses of Jupiter's moon Io: every day or two Io would go into Jupiter's shadow and later emerge from it. Rømer could see Io blink off and then later blink on, if Jupiter happened to be visible. Io's orbit seemed to be a kind of distant clock, but one which Rømer discovered ran fast while Earth was approaching Jupiter and slow while it was receding from the giant planet. Roemer measured the cumulative effect: by how much it eventually got ahead and then eventually fell behind. He explained the measured variation by positing a finite velocity for light.
See also
Fizeau-Foucault Apparatus, Galileo Galilei, Michelson Morley experiment
External links and References
- Group Velocity experiment: http://news.bbc.co.uk/hi/english/sci/tech/newsid_841000/841690.stm
- Java applet demonstrating group velocity information limits: http://www.netspace.net.au/~gregegan/APPLETS/20/20.html
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Speed of light."
| The following table is compiled from various sources, across various languages. When English abbreviations or acronyms come from a non-English source, this is noted. | |||
| Entry | Source | Expression | Field |
| LI | English | Light Infantry | N/A |
Source: compiled by the editor, based on several corpora (additional references). | |||
Synonyms: LightSynonyms: abstemious (adj), clean (adj), clear (adj), diet(a) (adj), easy (adj), faint (adj), flimsy (adj), friable (adj), idle (adj), light(a) (adj), light-colored (adj), lightheaded (adj), light-headed (adj), lightsome (adj), lite (adj), loose (adj), low-cal (adj), promiscuous (adj), sandy (adj), scant(p) (adj), short (adj), sluttish (adj), swooning (adj), tripping (adj), unaccented (adj), unclouded (adj), wakeful (adj), wanton (adj), weak (adj), lightly (adv), brightness (n), brightness level (n), igniter (n), ignitor (n), illumination (n), light source (n), lighter (n), lighting (n), lightness (n), luminance (n), luminosity (n), luminousness (n), spark (n), sparkle (n), visible light (n), visible radiation (n), alight (v), dismount (v), fall (v), fire up (v), get down (v), get off (v), ignite (v), illume (v), illuminate (v), illumine (v), light up (v), perch (v), unhorse (v). (additional references) |
| Antonyms: heavy (adj), dark (n), extinguish (v). (additional references) |
| Context | Synonyms within Context (source: adapted from Roget's Thesaurus). |
Calefaction | Fire; set fire to, set on fire; kindle, enkindle, light, ignite, strike a light; apply the match to, apply the torch to; rekindle, relume; fan the flame, add fuel to the flame; poke the fire, stir the fire, blow the fire; make a bonfire of. |
Cheerfulness | Adjective: cheerful; happy; cheery, cheerly; of good cheer, smiling; blithe; in spirits, in good spirits; breezy, bully, chipper; in high spirits, in high feather; happy as the day is long, happy as a king; gay as a lark; allegro; debonair; light, lightsome, light hearted; buoyant, debonnaire, bright, free and easy, airy; janty, jaunty, canty; hedonic; riant; sprightly, sprightful; spry; spirited, spiritful; lively, animated, vivacious; brisk as a bee; sparkling, sportive; full of play, full of spirit; all alive. |
Descent | Dismount, alight, light, get down; swoop; stoop; fall prostrate, precipitate oneself; let fall. |
Facility | Unembarrassed, disburdened, unburdened, disencumbered, unencumbered, disembarrassed; exonerated; unloaded, unobstructed, untrammeled; unrestrained; (free); at ease, light. |
Fuel | Brand, torch, fuse; wick; spill, match, light, lucifer, congreve, vesuvian, vesta, fusee, locofoco; linstock. |
Impurity | Unchaste, light, wanton, licentious, debauched, dissolute; of loose character, of easy virtue; frail, gay, riggish, incontinent, meretricious, rakish, gallant, dissipated; no better than she should be; on the town, on the streets, on the pave, on the loose. |
Interpretation | Acception, acceptation, acceptance; light, reading, lection, construction, version. |
Irresolution | Vacillating; Verb: unsteady; (changeable); unsteadfast, fickle, without ballast; capricious; volatile, frothy; light, lightsome, light-minded; giddy; fast and loose. |
Opening | Embrasure, window, casement; abatjour; light; sky light, fan light; lattice; bay window, bow window; oriel; dormer, lantern. |
Rarity | Adjective: rare, subtile, thin, fine, tenuous, compressible, flimsy, slight; light; cavernous, spongy. (hollow). |
Smallness | Adjective: small, little; diminutive; (small in size); minute; fine; inconsiderable, paltry; (unimportant); faint; (weak); slender, light, slight, scanty, scant, limited; meager; (insufficient); sparing; few; low, so-so, middling, tolerable, no great shakes; below par, under par, below the mark; at a low ebb; halfway; moderate, modest; tender, subtle. |
State | Tone, tenor, turn; trim, guise, fashion, light, complexion, style, character. |
Unimportance | Trifling, trivial; slight, slender, light, flimsy, frothy, idle; puerile; (foolish); airy, shallow; weak; powerless; frivolous, petty, niggling; piddling, peddling; fribble, inane, ridiculous, farcical; finical, finikin; fiddle-faddle, fingle-fangle, namby-pamby, wishy-washy, milk and water. |
Velocity | Lightning, greased lightning, light, electricity, wind; cannon ball, rocket, arrow, dart, hydrargyrum, quicksilver; telegraph, express train; torrent. |
Wit | Adjective: witty, attic; quick-witted, nimble-witted; smart; jocular, jocose, humorous; facetious, waggish, whimsical; kidding, joking, puckish; playful; merry and wise; pleasant, sprightly, light, spirituel, sparkling, epigrammatic, full of point, ben trovato; comic. |
| Source: adapted from Roget's Thesaurus. | |
| Domain | Usage | |
Screenplays | That beautiful stage that you were gonna build for me. You were gonna light it with nothing but candles (The Sweet Hereafter; writing credit: Atom Egoyan) Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.Raymond: Total protonic reversal (Ghostbusters; writing credit: Dan Aykroyd and Harold Ramis.) From that point on, the guys looked at me in a completely different light. (There's Something About Mary; writing credit: Ed Decter; John J. Strauss) But it was not the end. I felt light in me again (The Lord of the Rings: The Two Towers; writing credit: Frances Walsh) Do you leave the light on after bedtime (The Green Mile; writing credit: Frank Darabont. Based on the novel by Stephen King.) | |
Lyrics | The calliope crashed to the ground and she was blinded by the light, (Blinded By The Light (Bruce Springsteen); performing artist: MANFRED MANN) I can see paradise by the dashboard light (Paradise By The Dashboard Light; performing artist: Meat Loaf) When its right, the light just comes shinin thru (Caught Up in You; performing artist: 38 Special) When she woke up late in the morning light (All That She Wants; performing artist: Ace Of Base) You finally see the light (Amazing; performing artist: Aerosmith) | |
Clever | To light a candle is to cast a shadow. (references; author: unknown) Better to light a candle, than to curse the darkness. (references; author: unknown) It is better to light a candle than curse the darkness. (references; author: unknown) Both breasts are equal and reactive to light and accommodation. (references; author: unknown) The light at the end of the tunnel has been turned off due to budget cuts. (references; author: unknown) | |
Tongue Twisters | It's the right light with the glimmer in the mirror. (references; author: unknown) Yellow arrows frilled with reefed leaves are rarely light. (references; author: unknown) | |
Movie/TV Titles | Columbo: By Dawn's Early Light (1974) The Light Fantastick (1974) Light (1973) The Light from the Second Story Window (1973) Red Light in the White House (1971) | |
Song Titles | Light My Fire (performing artist: The Doors) Light My Fire (performing artist: Jose Feliciano) Ray Of Light (performing artist: Madonna) Blinded By The Light (performing artist: Manfred Mann's Earth Band) Paradise By The Dashboard Light (performing artist: Meat Loaf) | |
Source: compiled by the editor from various references; see credits. | ||
| Domain | Title | ||
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High Tech |
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Source: compiled by the editor from various references; see credits. | |||
| Thumbnail | Description & Credit | Thumbnail | Description & Credit |
 | Shows poster of artistically rendered landscape scene with woman standing in foreground holding a sword - white light shines down on woman with slogans: "Cancer Is Curable," "Enlist In The Women's Field Army," "American Society For The Control Of Cancer". Credit: Unknown photographer/artist. |  | Seen is a "beam of light" traveling along fiber optics for photodynamic therapy for use in an operating room. Its source is a laser beam which is split at two different stages to create the proper "therapeutic wavelength". The patient has been given a photo sensitive drug containing cancer killing substances which are absorbed by cancer cells. During the surgery, the light beam is positioned at the tumor site, which then activates the drug that kills the cancer cells, thus photodynamic therapy. Credit: John Crawford (photographer). |
 | A blood test can detect the presence of antibodies produces by an infected patient by binding chemicals to the antibodies that fluoresce green under UV light. Credit: CDC. |  | M. tuberculosis is an acid-fast bacterium (AFB), and is therefore, undetectable when stained using a Gram stain technique. However, using this method, the M. tuberculosis bacteria glow yellow under ultraviolet light microscopy. Credit: CDC. |
 | Terra First Light Images. Credit: NASA. |  | Fireworks of Star Formation Light Up a Galaxy. Credit: NASA. |
 | Light and Shadow in the Carina Nebula. Credit: NASA. |  | Pictures taken in infrared and visible light by the Hubble telescope recount a vivid story of ... Credit: NASA. |
 | The Egg Nebula, also known as CRL 2688, is shown on the left as it appears in visible light ... Credit: NASA. |  | First direct look, in visible light, at a lone neutron star (RX J185635-3754). (Produced with the Wide-Field Planetary Camera 2, Hubble Space Telescope.). Credit: NASA. |
Source: pictures compiled by the editor from various references; see picture credits. | |||
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| "Light Game" by Lucian Slatineanu Commentary: "Just playing with some light." | "Light bulb" by Jason Hart Commentary: "An exterior light on the porch, taken at night." |
Source: photographs selected by the editor, with permission from the photographers. | |
| Play | Caption | Play | Caption |
 | Arpeggiated guitar with solo guitar and light strings in background. | | Light pizzicato and ambient sounds creating a pleasant mood. |
| Typical Latin-style bass and light percussion with guitar solo. | | Digital piano arpeggios with light digital water drops in background. |
| Jamaican-influenced example using synthesized flute, light percussion, guitar, and piano. | | Light synthesized piece featuring lots of reverb on eh keyboards. |
| Light almost floating ambient texture featuring a busy synthesized melody. | | A single electric guitar note with light distortion. |
| Brief swishing sound from star wars light saber . | ||
| Source: compiled by the editor from various references; see credits. | |||
| Author | Quotation |
Francis Bacon | God's first creature, which was light. |
Henry David Thoreau | Let nothing come between you and the light. |
John Gay | Shadow owes its birth to light. |
John Heywood | Many hands make light work. |
John Milton | Doth God exact day-labor, light denied? |
Michelangelo | I live and love in God's peculiar light. |
Norman O. Brown | Love without attachment is light. |
Robert Burton | I light my candle from their torches. |
Thomas p Kempis | Love makes everything that is heavy light. |
Source: compiled by the editor from various references. | |
| Author | Date | Quotation |
John Locke | 1690 | And thus much may suffice to shew, that as far as we have any light from history, we have reason to conclude, that all peaceful beginnings of government have been laid in the consent of the people. (Second Treatise of Government) |
US Declaration of Independence | 1776 | Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn, that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed. (reference) |
Treaty of Versailles | 1919 | Armament (guns, machine guns, light machine guns, bombdropping apparatus, torpedo-dropping apparatus, synchronisation apparatus, aiming apparatus). (reference) |
Brown v. Board of Education | 1954 | We must consider public education in the light of its full development and its present place in American life throughout [347 U.S. 483, 493] the Nation. (reference) |
John F. Kennedy | 1961 | The energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it--and the glow from that fire can truly light the world. (reference) |
Dr. Martin Luther King, Jr. | 1963 | This momentous decree came as a great beacon light of hope to millions of Negro slaves who had been seared in the flames of withering injustice. (Delivered on the steps at the Lincoln Memorial in Washington D.C. on August 28, 1945) |
Source: compiled by the editor from various references. | ||
| Title | Author | Quote |
Emma | Austen, Jane | In no other light could you have been more to me than a common acquaintance |
Faces in the Fire | Carroll, Lewis | The pictures, with their ruddy light, Are changed to dust and ashes white, And I am left alone with night |
A Christmas Carol | Dickens, Charles | Light flashed up in the room upon the instant, and the curtains of his bed were drawn |
Scarlet Letter | Hawthorne, Nathaniel | The sensitive clergyman shrunk, with nervous dread, from the light missile |
Les Miserables | Hugo, Victor | Were this not so it would be superior to intelligence, and the beast would be in possession of a purer light than man. |
Portrait of the Artist as a Young Man | Joyce, James | At last, after a bend of the road, I spied a little cottage with a light in the window |
King Richard III | Shakespeare, William | Ay, gentle cousin, were it light enough |
Grapes of Wrath | Steinbeck, John | It rode hard and light. |
Gulliver's Travels | Swift, Jonathan | That he discovered two staples upon one side, which was all of boards, without any passage for light. |
Walden | Thoreau, Henry David | This was not the light in which I hoed them |
Source: compiled by the editor from various references. | ||
| Subject | Topic | Quote |
Health | Perhaps you need a hallway light. (references) | |
Eat a light meal before treatment. (references) | ||
Light infections may be asymptomatic. (references) | ||
Business | Sales in light commercial vehicles in 1999 was 5642 vehicles. (references) | |
The variety of light industrial and consumer goods increased. (references) | ||
Sales prospects may exist for foreign light commercial vehicles. (references) | ||
Civil Liberties | Macedonia | The parliament building suffered light damage. (references) |
Ukraine | The police arrested several hundred demonstrators, many of whom later were acquitted or given light sentences. (references) | |
Tanzania | Even the government-owned newspaper regularly reports events that portray the Government in an unflattering light. (references) | |
Economic History | Djibouti | Light industries simply do not exist in Djibouti. (references) |
Mexico | General Motors operates a light truck assembly plant in Silao. (references) | |
India | In this light, the current volume of organized retailing is small. (references) | |
Human Rights | Nicaragua | However, the judge gave them a light sentence. (references) |
Morocco | If the infraction is minor and not contested, the judge may order the defendant released or impose a light sentence. (references) | |
Israel and the occupied territories | The IDF had fired two flechette tank shells, and one armor-piercing tank round at the tent after hearing distant light gunfire. (references) | |
Minorities | Romania | The victims appealed to the European Court of Justice, arguing that the sentences were too light at 2 to 6 years. (references) |
Cyprus | A previously unknown Greek Cypriot nationalist organization claimed responsibility for an arson attack on a mosque in the south in August 1999. Damage was light. (references) | |
Political Economy | CHILE | The automobile and light truck industry is the subject of trade-related investment measures. (references) |
Political Rights | Belarus | This was a particular concern in light of the total domination of voting commissions, which were charged with conducting the election, by regime supporters. (references) |
Trade | Qatar | Some may be activated in light of Qatar's WTO membership. (references) |
Kenya | There is relatively light trading in commercial paper, and there now exists a secondary market in government paper. (references) | |
Travel | Philippines | Light entertainment is not unusual. (references) |
Philippines | Light suits and dresses are appropriate for women. (references) | |
Chad |
