The region of the electromagnetic spectrum that the human eye is capable of perceiving is called the visible spectrum. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. There are no exact limits on the visible spectrum: the typical human eye will respond to wavelengths from 380 to 750 nm, although in rare cases some people may be able to perceive wavelengths from 310 to 1050 nm. Arcs Irises are an example of refraction in the visible spectrum. The "most visible color" is yellow.
The corresponding wavelength in water and other media is reduced by a factor equal to the refractive index. In terms of frequency, this corresponds to a band in the range of values between 450 and 750 nm. A light-adapted eye generally has a maximum sensitivity value of 555 nm, in the green region of the visible spectrum. The spectrum, however, does not contain all the colors that the human eyes and brain can distinguish; brown, pink, magenta, gold, silver, and black are absent, for example, because they require the mixing of multiple wavelengths.
The wavelength visible to the eye also passes through an optical window, the very attenuated region of the electromagnetic spectrum passing through the Earth's atmosphere (despite the fact that blue light is more scattered than red light, which is why the color of the sky). The response of the human eye is defined by a subjective test, but the atmospheric windows are defined by physical measurements. The visible window is so named because it superimposes the visible human response onto the spectrum; the infrared window is tied to the human response window and the mid-infrared wavelength, the far-infrared wavelength are very far from the human response region.
The eyes of many species perceive wavelengths different from those of the visible spectrum of the human eye. For example, many insects such as bees can see ultraviolet light which is useful for finding nectar in flowers. For this reason, the reproductive successes of plant species whose life cycles are linked to insect pollination depend on their producing ultraviolet emission, rather than on the color apparent to human eyes.
In the 13th century, Roger Bacon theorized that rainbows were produced by a process similar to the passage of light through a glass of water.
The first explanation of the visible spectrum comes from Isaac Newton, who wrote in his Optics about his studies on the dispersion and grouping of white light through the use of prisms. Newton first used the word spectrum (from the Latin for "appearance" or "appearance") in 1671 when describing his experiments in optics. Newton observed that when a narrow beam of sunlight strikes a triangular glass prism at an angle, some is reflected and some passes through the glass, showing different bands of colors. Newton's hypothesis was that light was made up of corpuscles (particles) of different colors and that the difference in colors was due to the difference in speed of each of them, so that in a transparent medium, red light was faster than violet light. The result is that red light was bent (refracted) less than violet light when it passed through the prism, creating the color spectrum.
Newton divided the spectrum into seven colors: red, orange, yellow, green, blue, indigo, and violet, inspired by a belief from ancient Greek sophists that there was a connection between colors, musical notes , days of the week, and known objects in the solar system. This seven color scheme has received criticism such as that of Isaac Asimov,