It's called infrared light outside one end of the spectrum,
and ultraviolet light outside the other end.,
It is called Visible light Spectrum.
You probably mean "Spectrum".
Discontinuous Spectra, Fraunhofer lines
I would call this just "the visible spectrum." http://en.wikipedia.org/wiki/Visible_spectrum
No reason. Light is an electromagnetic wave so you can call any part of the spectrum either.
the electromagnetic spectrum
White light can be split up into lots of different coloured light waves using a prism. We call this range of colours the visible spectrum.
Is spectrum too simplistic an answer?
White light can be split up into lots of different coloured light waves using a prism. We call this range of colours the visible spectrum.
The visible portion of electromagnetic spectrum is called the visible light and is the electromagnetic wave with the wavelength between 380 - 740 nm.
No sure what you mean by "the reason." Electromagnetic waves exist in our Universe. Our eyes are able to detect a small fraction of the spectrum of these waves, and we call that small fraction of the spectrum, "light." In other words, the reason that light is an EM wave is because it IS.
The visible portion of the Electromagnetic Spectrum. Visibility to the human eye is determined by the Frequency (or wavelength) of the light.