Red: Wavelength of Reflection

Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm.[2] Longer wavelengths than this are called infrared (below red), and cannot be seen by the naked human eye. Red is used as one of the additive primary colors of light, complementary to cyan, in RGB color systems. Red is also one of the subtractive primary colors of RYB color space but not CMYK color space.
Etymology and definitions

The word red comes from the Old English rēad.[4] Further back, the word can be traced to the Proto-Germanic rauthaz and the Proto-Indo European root reudh-. In Sanskrit, the word rudhira means red or blood. In the English language, the word red is associated with the color of blood, certain flowers (e.g. roses), and ripe fruits (e.g. apples, cherries). Fire is also strongly connected, as is the sun and the sky at sunset. Healthy light-skinned people are sometimes said to have a "ruddy" complexion (as opposed to appearing pale). After the rise of socialism in the mid-19th century, red was used to describe revolutionary movements.[5]
[edit]In science

Artificial red poppies
[edit]Colorimetry, color science, photography
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of approximately 630–700 nm.[2] Longer wavelengths than this are called infrared, or below red and cannot be seen by human eyes.[6] Red's wavelength has been an important factor in laser technologies as red lasers, used in early compact disc technologies, are being replaced by blue lasers, as red's longer wavelength causes the laser's recordings to take up more space on the disc than blue lasers.[7] A main theory for why primates developed sensitivity to red, is that it allowed ripe fruit to be distinguished from unripe fruit and inedible vegetation.[8]...