Light forms a continuous spectrum but human eyes are only capable of seeing the spectrum of visible light corresponding to “a wavelength range of 400 to 700 nanometers and a color range of violet through red” (Kusterer, 2007). This means that normal human vision has a limited visual range and can perceive only to such an extent. Among the visible colors, violet has the shortest wavelength at 400 nm. Indigo follows it closely at around 445 nm while the wavelength for the blue light that gives color to the sky measures 475 nm. Green comes next with about 510 nm while yellow follows closely at 570 nm and orange at 590 nm. The last visible color in the spectrum is red, with a wavelength range of 650 nm through 700 nm. The colors with relatively longer wavelengths, red and orange, are usually “less efficiently scattered” so they are more readily seen at sunrise and sunset. Blue and violet light, on the other hand, are normally scattered. So far, this is the visible and observed spectrum of light of which the normal human eye is capable. (Kusterer, 2007)
Since light is a continuous spectra, there are numerous wavelengths in the electromagnetic spectrum that normal human vision cannot perceive. Some of this light energy includes those with wavelengths that are too short for the human eye to see. These include ultraviolet light and the spectra of light that causes sunburns and the same light used for skin tanning.
Another spectra of light which remains invisible to the human eye includes those with wavelengths that are considered too long for normal human vision to perceive. These include infrared light and those that make adjacent things hot such as light energy coming from the campfire or stove burner. Light spectra with very long wavelengths are usually significant in that they “radiate heat to outer space” for if they do not do so, the solar energy absorbed by the Earth would remain trapped and continue to heat the planet. (Kusterer,