What Is the Visible Light Spectrum?

The visible light spectrum is the section of the electromagnetic radiation spectrum that is visible to the human eye. Essentially, that equates to the colors the human eye can see. It ranges in wavelength from approximately 400 nanometers (4 x 10 ^-7 m, which is violet) to 700 nm (7 x 10^-7 m, which is red). It is also known as the optical spectrum of light or the spectrum of white light.

Wavelength and Color Spectrum Chart

The wavelength of light, which is related to frequency and energy, determines the perceived color. The ranges of these different colors are listed in the table below. Some sources vary these ranges pretty drastically and their boundaries are somewhat approximate, as they blend into each other. The edges of the visible light spectrum blend into the ultraviolet and infrared levels of radiation.

How White Light Is Split Into a Rainbow

Most light that we interact with is in the form of white light, which contains many or all of these wavelength ranges. Shining white light through a prism causes the wavelengths to bend at slightly different angles due to optical refraction. The resulting light is split across the visible color spectrum.

This is what causes a rainbow, with airborne water particles acting as the refractive medium. The order of wavelengths can be remembered by the mnemonic "Roy G Biv" for red, orange, yellow, green, blue, indigo (the blue/violet border), and violet. If you look closely at a rainbow or spectrum, you might notice that cyan also appears between green and blue. Most people cannot distinguish indigo from blue or violet, so many color charts omit it.

By using special sources, refractors, and filters, you can get a narrow band of about 10 nanometers in wavelength that is considered monochromatic light. Lasers are special because they are the most consistent source of narrowly monochromatic light that we can achieve. Colors consisting of a single wavelength are called spectral colors or pure colors.

Colors Beyond the Visible Spectrum

The human eye and brain can distinguish many more colors than those of the spectrum. Purple and magenta are the brain's way of bridging the gap between red and violet. Unsaturated colors such as pink and aqua are also distinguishable, as well as brown and tan.

However, some animals have a different visible range, often extending into the infrared range (wavelength greater than 700 nanometers) or ultraviolet (wavelength less than 380 nanometers). For example, bees can see ultraviolet light, which is used by flowers to attract pollinators. Birds also can see ultraviolet light and have markings that are visible under a black (ultraviolet) light. Among humans, there is variation between how far into red and violet the eye can see. Most animals that can see ultraviolet can't see infrared.