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How do we see color? Sensing light
We perceive color when the different wavelengths composing white light are selectively interfered with by matter (absorbed, reflected, refracted, scattered, or diffracted) on their way to our eyes, or when a non-white distribution of light has been emitted by some system.
Visible light is merely a small part of the full electromagnetic spectrum, which extends from cosmic rays at the highest energies down through gamma rays, X- rays, the ultraviolet, the visible, the infrared, and radio waves to induction-heating and electric-power-transmission frequencies at the lowest energies. Note that this is the energy per quantum (photon if in the visible range) but not the total energy; the latter is a function of the intensity in a beam.
We can detect the range of light spectrum from about 400 nanometers (violet) to about 700 nanometers (red). We perceive this range of light wavelengths as a smoothly varying rainbow of colors -- the visual spectrum.
