Welcome to Northwest Firearms
Join our community, sign up for free today!
Sign Up


Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is visible to the human eye and is responsible for the sense of sight. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), or 4.00 × 10−7 to 7.00 × 10−7 m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range of roughly 430–750 terahertz (THz).
The main source of light on Earth is the Sun. Sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the energy used by living things. Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps. With the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence. For example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey.
The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarisation, while its speed in a vacuum, 299,792,458 metres per second, is one of the fundamental constants of nature. Visible light, as with all types of electromagnetic radiation (EMR), is experimentally found to always move at this speed in a vacuum.
In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. Like all types of light, visible light is emitted and absorbed in tiny "packets" called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.
^ CIE (1987). International Lighting Vocabulary. Number 17.4. CIE, 4th edition. ISBN 978-3-900734-07-7.
By the International Lighting Vocabulary, the definition of light is: “Any radiation capable of causing a visual sensation directly.”
^ Pal, G. K.; Pal, Pravati (2001). "chapter 52". Textbook of Practical Physiology (1st ed.). Chennai: Orient Blackswan. p. 387. ISBN 978-81-250-2021-9. Retrieved 11 October 2013. The human eye has the ability to respond to all the wavelengths of light from 400–700 nm. This is called the visible part of the spectrum.
^ Buser, Pierre A.; Imbert, Michel (1992). Vision. MIT Press. p. 50. ISBN 978-0-262-02336-8. Retrieved 11 October 2013. Light is a special class of radiant energy embracing wavelengths between 400 and 700 nm (or mμ), or 4000 to 7000 Å.
^ Gregory Hallock Smith (2006). Camera lenses: from box camera to digital. SPIE Press. p. 4. ISBN 978-0-8194-6093-6.
^ Narinder Kumar (2008). Comprehensive Physics XII. Laxmi Publications. p. 1416. ISBN 978-81-7008-592-8.

View More On Wikipedia.org
  1. gun.deals

    HK P30 V1 Light LEM 40 S&W 3.85" 13 Rd with 2 Magazines - $499.88

    HK P30 V1 Light LEM 40 S&W 3.85" 13 Rd with 2 Magazines - $499.88 (Free Store Pickup)
  2. gun.deals

    Viridian V200 Manual Zoom Green LED Light w/3 Mounts Pressure Switch - $79 shipped

    Viridian V200 Manual Zoom Green LED Light with 3 Mounts and Pressure Switch, 250 yd. - $79 shipped
  3. gun.deals

    iPROTEC Green Laser/LED Light Combo - $69.99

    iPROTEC Green Laser/LED Light Combo - $69.99 (Free S/H over $99 w/code "7TREAT")
  4. M

    Glock 29 Tac Light Recommendations

    I have a Glock 29 with an extended barrel (4.6") that I would like to put a tac light on. My current Kenai Chest Holster from Gunfighters Inc. does not accommodate a tac light, so I will be ordering a new holster. The holster are Kydex and they have several light options. Which of the light...
  5. Red1

    WTS WA  Tactical tailor fight light operator pack

    New price $99 This tactical tailors fight light operator pack in multicam its like new bought it on a whim and never really used it. This specific bag is 159.95+shipping+ tax on the tactical tailor website. I paid closer to 175 I believe with tax and what not. Anyways it's an Awsome bag but...
  6. RicInOR

    OR: Red Light Cameras NOW Catch You Speeding too

    Red light cameras can catch you speeding starting Thursday "The city of Beaverton has a system that allows its four intersection cameras to capture speeds." See also: 8 Really Bad Laws That Just Went Into Effect
  7. R

    WTS/WTT OR  New - Streamlight TLR-4 Tac Light with Red Laser, Black

    Streamlight TLR-4 Tac Light with laser - Brand new unused. Selling because I decided i don't need the laser option - Red laser - Easy to operate and switch between light only, laser only or light and laser combo Willing to trade for TLR-1 HL, Surefire X300 or $110 cash
  8. gun.deals

    UTG 95lumen Combat Xenon Weapon Light with Integral Mount - $14.23 + FS over $25

    UTG 95lumen Combat Xenon Weapon Light with Integral Mount - $14.23 + FS over $25
  9. B

    Tactical light recommendations anyone?

    Looking for something that is name brand, pressure button activated (press to turn on, no click), long gun mountable, and 500 Lumens and up, preferably 800+ Lumens. The streamlight pro tac series seem alright?
  10. Will_White

    Good light and laser combo for around 200$ for AR?

    I'm looking to get a light and laser combo for my AR. I've seen a lot of recommended pistol style combos in that price range but I haven't been able to find any with a remote switch, recommendations?
  11. gun.deals

    Laser Genetics ND3-P Subzero Pistol Beam Light - $59.99 + Free Shipping

    Laser Genetics ND3-P Subzero Pistol Beam Light - $59.99 + Free Shipping
  12. gun.deals

    UTG 95lumen Combat Xenon Weapon Light with Integral Mount - $15.70 + FS over $25

    UTG 95lumen Combat Xenon Weapon Light with Integral Mount - $15.70 + FS over $25
  13. HariKh

    WTS OR  $200 Surefire XC1 weapons light and Bravo light bearing holster glock 19/23/32

    Brand new in box Surefire XC1 weapons light never used. Will include a Bravo Concealment "DOS-L" light bearing inside the waistband holster. $200 OBO located in Eugene Five four one-nine six eight-six six six three