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light
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.
Like New HRT AWLS weapon light. Comes with all factory items including adjustable tail switch, battery and charging cable. There is a standard push button tailcap underneath the omni switch which is removable easily. This light is very bright with 1500 Lumens and 100,000 Candela. It just didnt...
I no longer have the AR22, so up for sale is a like new BoreBuddy 22lr Light Adjustable Bolt Weight kit and plug. It's designed to eliminate bolt bounce on the CMMG type .22 bolt carriers and the plug ensures forward pressure to remove bolt play.
$60 picked up from Portland.
-R
Forester co-ax single stage press with light,
B4- B5 version, comes with the large and small shell plates, also comes with the shell holder adapter plate, also has 10 lock rings, and two short action customs special lock rings with the Justine marks, also has the priming plug on top of the...
I believe this is 1.0 version. I've had it for a couple years and mounted it once but I just didn't use it. It's in excellent shape. It comes with the original mount as well as an arisaka mount that I put on it. This was the standard kit with push button on the end of the light. Later I...
Selling my M&P.
It has on it:
HOLOSUN SCS-MP2-GR Green Multi-Reticle 2 MOA Dot & 32 MOA Circle Pistol Sight
Streamlight 69260 TLR-1 HL 1000-Lumen Weapon Light
It will come with 8 total magazines. 5 factory 17 round steel and 3 21 round ETS polymer mags.
Also included is the factory hard...
Olight BALDR-RL Sight & Light, in great condition.
I have everything it came with, including the unused Olight batteries.
Please PM me for a response.
Willing to ship on your dime.
Hello,
I'm looking for an Arisaka Offset mount for a scout type light that is Keymod compatible.
They seem to be out of stock everywhere.
Anybody have one they want to part with or know where a guy can find one?
Thank you
Surefire M500 rifle length handguard set, perfect for your retro build with the 1990 LAPD SWAT vibe. Fully functional with covers for both the momentary and constant on switch intact. This is the non nav light model. Bad acting not included. $100
Did some Cleaning and honestly forget where I got this from, most likely an old trade. I am honestly unsure of what model this is. This is I guess a more retro surefire light, as its not an LED head.
Has picatinny mount attached, could use a new battery. Make me an offer, I dont know what its...
Wts surefire x300b good condition. Looking for 250 or trade for a Holosun rmsc footprint optic Preferably green. Maybe cash on my end depending on optic. Pm for info or pics thanks. Added charger and rechargeable batteries.
Like new Tikka super light 308 , stainless fluted barrel,limbsaver, extra mag,3x9x50 Burris scope, picatany Mount, safari sling,ammo, Tikka bag, 1500 set up asking 1000,only been sighted in 22 rds though it
Curious if anyone has been to shows here and how tight they are with security? Is it like getting on amtrac or do they pat/search/metal detect? Prefer to keep that thang on me but if I have to a knife behind the belt buckle will do
Brand new.
Safariland RH retention holster for Springfield XD with light. M300/TLR-1
Has paddle attached, belt slide and hardware included, no box
Unused, bought the wrong holster & cant return it
$45
Will trade for
- holster for GP100 3"
-12ga ammo (any)
- 9mm ammo (practice or...
An oldie but goody. Has scuffs and scratches normal for a scope of its age. Light rust on the caps. Glass is nice and clear. Will ship for an extra $15.
Trade interests are:
Large Rifle primers
Reloder 22
H4895
IMR 4895
IMR 4198
.284 160gr Nosler Accubonds
.308 125gr Ballistic Tips
Clearing out some old stuff. 2 b5 sopmod bravos (one foilage green, one coyote) $30 each
a b5 type 23 grip coyote $15
T rex arms 1913 light mount $30
B&t mp5 aimpoint micro mount brand new never used $50
Prices firm, would trade for an fde sba3 or an mlok tango down stubby. Thanks guys!