What is light?

  • (noun): (physics) electromagnetic radiation that can produce a visual sensation.
    Example: "The light was filtered through a soft glass window"
    Synonyms: visible light, visible radiation
    See also — Additional definitions below


Visible light (commonly referred to simply as light) is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has a wavelength in the range of about 380 nanometres to about 740 nm – between the invisible infrared, with longer wavelengths and the invisible ultraviolet, with shorter wavelengths.

Read more about Light.

Some articles on light:

Historical Theories About Light, in Chronological Order - Electromagnetic Theory As Explanation For All Types of Visible Light and All EM Radiation
... 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 ... This was the first evidence that light was related to electromagnetism ... In 1846 he speculated that light might be some form of disturbance propagating along magnetic field lines ...
Flash - Light
... source of very short and extremely bright flashes of light Arc flash, an electrical explosion Lightning, a natural phenomenon Muzzle flash, the visible light of the muzzle blast ...
Color Temperature - Color Rendering Index
... index (CRI) is a method to determine how well a light source's illumination of eight sample patches compares to the illumination provided by a reference source ... and CCT give a numerical estimate of what reference (ideal) light source best approximates a particular artificial light, and what the difference is ...
Correlated Color Temperature - Motivation
... are the reference by which the whiteness of light sources is judged ... By analogy, nearly-Planckian light sources such as certain fluorescent or high-intensity discharge lamps can be judged by their correlated color temperature (CCT ... The question is what is the relationship between the light source's relative spectral power distribution and its correlated color temperature? ...
Speed Of Gravity - Lorentz Covariant Models
... than c would contradict the concept of local time (based on synchronization by light signals) and the principle of relativity ... wrote What would happen if we could communicate by signals other than those of light, the velocity of propagation of which differed from that of light? If, after having regulated our ... with a velocity a million times as great as that of light? However, in 1905 Poincaré calculated that changes in the gravitational field can propagate with the speed of light if it is presupposed that such a theory is ...

More definitions of "light":

  • (adj): (used of color) having a relatively small amount of coloring agent.
    Example: "Light blue"; "light colors such as pastels"; "a light-colored powder"
    Synonyms: light-colored
  • (noun): Public awareness.
    Example: "It brought the scandal to light"
  • (adj): Intended primarily as entertainment; not serious or profound.
    Example: "Light verse"; "a light comedy"
  • (noun): A condition of spiritual awareness; divine illumination.
    Example: "Follow God's light"
    Synonyms: illumination
  • (adj): Very thin and insubstantial.
    Example: "Light summer dresses"
    Synonyms: flimsy
  • (noun): A person regarded very fondly.
    Example: "The light of my life"
  • (verb): Cause to start burning; subject to fire or great heat.
    Example: "Light a cigarette"
    Synonyms: ignite
  • (adj): Of the military or industry; using (or being) relatively small or light arms or equipment.
    Example: "Light infantry"; "light cavalry"; "light industry"; "light weapons"
  • (adj): Psychologically light; especially free from sadness or troubles.
    Example: "A light heart"
  • (noun): Any device serving as a source of illumination.
    Synonyms: light source
  • (adj): (physics, chemistry) not having atomic weight greater than average.
    Example: "Light water is ordinary water"
  • (adj): Having little importance.
    Example: "Losing his job was no light matter"
  • (adj): Demanding little effort; not burdensome.
    Example: "Light housework"; "light exercise"
  • (noun): An illuminated area.
    Example: "He stepped into the light"
  • (adj): (of sleep) easily disturbed.
    Example: "In a light doze"; "a light sleeper"
    Synonyms: wakeful
  • (adj): Having relatively few calories.
    Example: "Light (or lite) beer"
    Synonyms: lite, low-cal
  • (noun): Mental understanding as an enlightening experience.
    Example: "He finally saw the light"; "can you shed light on this problem?"
  • (adj): Less than the correct or legal or full amount often deliberately so.
    Example: "A light pound"
    Synonyms: scant, short
  • (adj): Having a spongy or flaky texture; well-leavened.
    Example: "Light pastries"
  • (adj): Silly or trivial.
    Example: "Light banter"; "light idle chatter"
    Synonyms: idle
  • (adj): Used of vowels or syllables; pronounced with little or no stress.
    Example: "A syllable that ends in a short vowel is a light syllable"
    Synonyms: unaccented, weak
  • (adj): Designed for ease of movement or to carry little weight.
    Example: "Light aircraft"; "a light truck"
  • (noun): A particular perspective or aspect of a situation.
    Example: "Although he saw it in a different light, he still did not understand"
  • (adj): Not great in degree or quantity or number.
    Example: "A light sentence"; "a light accent"; "casualties were light"; "light snow was falling"; "light misty rain"; "light smoke from the chimney"
  • (adj): Moving easily and quickly; nimble.
    Example: "The dancer was light and graceful"; "walked with a light tripping step"
    Synonyms: lightsome, tripping
  • (adj): Of little intensity or power or force.
    Example: "The light touch of her fingers"; "a light breeze"
  • (adj): Weak and likely to lose consciousness.
    Example: "Felt light in the head"; "light-headed with wine"; "light-headed from lack of sleep"
    Synonyms: faint, swooning, light-headed, lightheaded
  • (noun): A visual warning signal.
    Example: "They saw the light of the beacon"; "there was a light at every corner"
  • (noun): Having abundant light or illumination.
    Example: "They played as long as it was light"
    Synonyms: lighting
  • (noun): Brightness and animation of countenance.
    Synonyms: sparkle, spark
  • (adj): Of comparatively little physical weight or density.
    Example: "A light load"; "magnesium is a light metal--having a specific gravity of 1.74 at 20 degrees C"
  • (verb): To come to rest, settle.
    Synonyms: alight, perch
  • (noun): A device for lighting or igniting fuel or charges or fires.
    Example: "Do you have a light?"
    Synonyms: lighter, igniter, ignitor
  • (adv): With few burdens.
    Example: "Experienced travellers travel light"
    Synonyms: lightly
  • (adj): Easily assimilated in the alimentary canal; not rich or heavily seasoned.
    Example: "A light diet"
  • (adj): Marked by temperance in indulgence.
    Example: "A light eater"; "a light smoker"; "ate a light supper"
    Synonyms: abstemious
  • (verb): Fall to somebody by assignment or lot.
    Synonyms: fall
  • (adj): (used of soil) loose and large-grained in consistency.
    Example: "Light sandy soil"
    Synonyms: friable, sandy
  • (adj): Characterized by or emitting light.
    Example: "A room that is light when the shutters are open"; "the inside of the house was airy and light"
  • (noun): The visual effect of illumination on objects or scenes as created in pictures.
    Example: "He could paint the lightest light and the darkest dark"
    Synonyms: lightness
  • (adj): (of sound or color) free from anything that dulls or dims.
    Example: "A light lilting voice like a silver bell"
    Synonyms: clean, clear, unclouded

Famous quotes containing the word light:

    As I drew a still fresher soil about the rows with my hoe, I disturbed the ashes of unchronicled nations who in primeval years lived under these heavens, and their small implements of war and hunting were brought to the light of this modern day.
    Henry David Thoreau (1817–1862)

    A lover may bestride the gossamers
    That idles in the wanton summer air,
    And yet not fall; so light is vanity.
    William Shakespeare (1564–1616)

    Oh! for a closer walk with God,
    A calm and heav’nly frame;
    A light to shine upon the road
    That leads me to the Lamb!
    William Cowper (1731–1800)