What is Visible Light?
The entire range of different kinds of light including the ones the human eye can see is called the electromagnetic spectrum. What we can see is called visible light. A rainbow shows the colors of visible light. Visible light has wavelengths that range between 400 and 700 nanometers (one billionth of a meter).
The visible portion of the spectrum is that which can be perceived by the human eye. It is slightly different for each person, although light with a wavelength of 400 to 700 nm is the usual definition. Some people are able to see visible light with wavelengths as short as 380 nm and as long as 780 nm. There is a repeatable experiment in which humans are able to perceive x-rays, which have wavelengths as short as 0.1 to 10 nm, but the visibility may derive from second-order interactions that produce light in the visible range.
