Normal human eye can receive wavelengths from 400 to 700 nanometers (nm), although some people may receive a wavelength of 380 to 780 nm. Eyes that have adapted to the light typically has a maximum sensitivity around 555 nm, in the green region of the optical spectrum. Mixing colors like pink or purple, not present in this spectrum because these colors will only be obtained by mixing several wavelengths.
Wavelengths of the visible spectral range defined by the optical windows, region of the electromagnetic spectrum that passes through the atmosphere. Electromagnetic radiation outside the optical wavelength range, or other transmission window is almost entirely absorbed by the atmosphere. It said optical window because humans can not reach from the outside of the optical spectrum. Infrared is located just outside the optical window, but can not be seen by human eyes.
Many species are able to see beyond the wavelength of the optical window. Bees and other insects can see ultraviolet light, which helps them find nectar in the flowers. Plant species depend on pollination by insects, so that contributed a great deal on their reproductive success is the presence of ultraviolet light, not the color of the flower show to man. Birds can see ultraviolet (300-400 nm).
The following limitations to the colors of the spectrum:
- Violet 380-450 nm
- Blue 450-495 nm
- Green 495-570 nm
- Yellow 570-590 nm
- Orange 590-620 nm
- Red 620-750 nm