What Is the Visible Spectrum?

The range of light from red to violet in a rainbow that is visible to the human eye is called the visible spectrum. Please take note of the emphasis on human! The visible spectrum is a tiny portion of something much larger: the electromagnetic spectrum. The only reason we have a special name for the visible part is because our particular anatomy is responsive to these particular wavelengths of light.

At one end of the electromagnetic spectrum, beyond red light with its longer wavelengths and lower frequencies, are even longer wavelengths and even lower frequencies of light that include infrared, microwaves, and radio waves. At the other end, beyond violet light with its shorter wavelengths of light and higher frequencies, there are even shorter wavelengths of light with even higher frequencies that include ultraviolet (UV) rays, X-rays, and gamma rays. Just as the borders between colors are fuzzy and arbitrary, so are the borders between these other parts of the electromagnetic spectrum. X-ray is just another “color,” like orange, in that it encompasses a range of wavelengths of light. It’s just that we humans can’t see this color.

It’s important to note that the visible spectrum as it is typically illustrated does not contain all the variations of colors that humans can see; rather, the spectrum is used to represent only the pure spectral colors made up of individual wavelengths of light. The bulk of the colors we see every day are actually made up of a mixture of wavelengths of light.