Light, Electromagnetic Spectrum
Light is so much a part of our everyday existence contributing to our quality of life, as well as a key enabler in photonics, solar power, and new lighting technologies, that the year 2015 has been declared by the UNESCO as the International Year of Light and Lighting Technologies.
Light has many different meanings depending upon the application.
When it is used to broadly describe optical radiation, it is defined as electromagnetic radiation with wavelengths between approximately 10 nm and 1 mm, i.e., a term that is used to describe the ultraviolet, visible, and infrared regions of the electromagnetic spectrum.
When it is used to describe a light stimulus, the International Lighting Vocabulary  gives the following two definitions: (1) It is a characteristic of all sensations and perceptions that is specific to vision, and (2) it is radiation...
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