The relationship between color and wavelength for light is inverse and direct: each specific color we perceive corresponds to a precise wavelength within the electromagnetic spectrum, measured in nanometers (nm). The wave on the top has a longer wavelength than the wave on the bottom. The electromagnetic spectrum encompasses all forms of electromagnetic radiation, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The optical spectrum is sometimes considered to be the same as the visible spectrum, but some authors define the term more broadly, to include the ultraviolet and infrared parts of the electromagnetic. The visible spectrum is the small portion of the electromagnetic spectrum that human eyes can detect, spanning wavelengths from approximately 380 nm (violet) to 700 nm (red).
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