Light

visible lightvisiblelight sourcewave theory of lightlight waveopticallight waveslight reflectionUndulatory Theory of Lightvisible spectrum
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.wikipedia
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Electromagnetic radiation

electromagnetic waveelectromagnetic waveselectromagnetic
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.

Human eye

eyeeyeseyeball
The word usually refers to visible light, which is the portion of the spectrum that can be perceived by the human eye.
The human eye is an organ that reacts to light and allows vision.

Infrared

IRnear-infraredinfra-red
Visible light is usually defined as having wavelengths in the range of 400–700 nanometers (nm), or 4.00 × 10 −7 to 7.00 × 10 −7 m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).
Infrared radiation (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light.

Ultraviolet

UVultraviolet lightultraviolet radiation
Visible light is usually defined as having wavelengths in the range of 400–700 nanometers (nm), or 4.00 × 10 −7 to 7.00 × 10 −7 m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).
Ultraviolet (UV) is electromagnetic radiation with wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays.

Electromagnetic spectrum

spectrumspectraspectral
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end.

Visible spectrum

visiblevisible lightspectrum
The word usually refers to visible light, which is the portion of the spectrum that can be perceived by the human eye.
Electromagnetic radiation in this range of wavelengths is called visible light or simply light.

Sunlight

sunshinesolar radiationnatural light
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.
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.

Electric light

light bulbelectric lightinglightbulb
With the development of electric lights and power systems, electric lighting has effectively replaced firelight.
An electric light is a device that produces visible light from electric current.

Fire

firesfire damageflame
Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps.
Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.

Bioluminescence

bioluminescentlight-producingluminescent
Some species of animals generate their own light, a process called bioluminescence.
Bioluminescence is the production and emission of light by a living organism.

Wavelength

wavelengthswave lengthsubwavelength
Visible light is usually defined as having wavelengths in the range of 400–700 nanometers (nm), or 4.00 × 10 −7 to 7.00 × 10 −7 m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).
Examples of waves are sound waves, light, water waves and periodic electrical signals in a conductor.

Frequency

frequenciesperiodperiodic
This wavelength means a frequency range of roughly 430–750 terahertz (THz).
Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.

Spectrum

spectraenergy spectrumspectral
The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum, 299,792,458 meters per second, is one of the fundamental constants of nature.
The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism.

Speed of light

clight speedspeed of light in vacuum
The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum, 299,792,458 meters per second, is one of the fundamental constants of nature.
Though this speed is most commonly associated with light, it is also the speed at which all massless particles and field perturbations travel in vacuum, including electromagnetic radiation and gravitational waves.

Optics

opticalopticoptical system
The study of light, known as optics, is an important research area in modern physics.
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it.

Photon

photonslight quantaincident photon
EMR in the visible light region consists of quanta (called photons) that are at the lower end of the energies that are capable of causing electronic excitation within molecules, which leads to changes in the bonding or chemistry of the molecule.
It is the quantum of the electromagnetic field including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force (even when static via virtual particles).

Visual perception

visionsighteyesight
The word usually refers to visible light, which is the portion of the spectrum that can be perceived by the human eye.
The human visual system is generally believed to be sensitive to visible light in the range of wavelengths between 370 and 730 nanometers (0.00000037 to 0.00000073 meters) of the electromagnetic spectrum.

Photomorphogenesis

photomorphogeniclight
Plant growth is also affected by the color spectrum of light, a process known as photomorphogenesis.
In developmental biology, photomorphogenesis is light-mediated development, where plant growth patterns respond to the light spectrum.

Microwave

microwavesmicrowave radiationmicrowave tube
In this sense, gamma rays, X-rays, microwaves and radio waves are also light.

Intensity (physics)

intensityintensitieslight intensity
The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum, 299,792,458 meters per second, is one of the fundamental constants of nature.
It is used most frequently with waves such as acoustic waves (sound) or electromagnetic waves such as light or radio waves, in which case the average power transfer over one period of the wave is used.

Cone cell

conesconecone cells
Furthermore, the rods and cones located in the retina of the human eye cannot detect the very short (below 360 nm) ultraviolet wavelengths and are in fact damaged by ultraviolet.
They respond differently to light of different wavelengths, and are thus responsible for color vision and function best in relatively bright light, as opposed to rod cells, which work better in dim light.

Rod cell

rodsrodrod cells
Furthermore, the rods and cones located in the retina of the human eye cannot detect the very short (below 360 nm) ultraviolet wavelengths and are in fact damaged by ultraviolet.
Rod cells are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells.

Photosynthesis

photosyntheticphotosynthesizephotosynthesizing
This process of photosynthesis provides virtually all the energy used by living things.
The surface of the leaf is coated with a water-resistant waxy cuticle that protects the leaf from excessive evaporation of water and decreases the absorption of ultraviolet or blue light to reduce heating.

Matter

corporealsubstancematerial
The effective velocity of light in various transparent substances containing ordinary matter, is less than in vacuum.
However it does not include massless particles such as photons, or other energy phenomena or waves such as light or sound.

Optical phenomena

optical phenomenonatmospheric phenomenaatmospheric phenomenon
The observation and study of optical phenomena such as rainbows and the aurora borealis offer many clues as to the nature of light.
Optical phenomena are any observable events that result from the interaction of light and matter.