Visible spectrum

The range of electromagnetic wavelengths detectable by human vision, approximately 380 to 700 nanometers. Its boundaries vary with observer and viewing conditions.

Electromagnetic radiation: Energy propagated through space as oscillating electric and magnetic fields, spanning radio waves to gamma rays. Visible light is one narrow band within this broader spectrum.
Photon: The quantum of electromagnetic radiation, carrying energy proportional to its frequency. Visible light can be described as photons whose energies correspond to visible wavelengths.
Spectroscopy: The study of interactions between matter and electromagnetic radiation as a function of wavelength or frequency. Visible spectroscopy measures absorption or emission within the human-visible band.
Ultraviolet: Electromagnetic radiation with wavelengths shorter than visible light and longer than X-rays. It borders the short-wavelength edge but is generally invisible to humans.
Wavelength: The distance between successive corresponding points of a wave, such as adjacent crests. Wavelength distinguishes positions across the visible spectrum.
Frequency: The number of cycles of a periodic wave passing a point per unit time. Frequency increases as wavelength decreases across visible light.
Prism: A transparent optical element that refracts light, often separating wavelengths by angle. Dispersion through a prism turns mixed visible light into a spectrum.
Infrared: Electromagnetic radiation with wavelengths longer than visible light and shorter than microwaves. It borders the long-wavelength edge and is perceived chiefly as heat, not color.
Photopic vision: Human vision under well-lit conditions, mediated chiefly by cone photoreceptors. Cone sensitivity determines how bright different visible wavelengths appear in daylight.
Refractive index: A measure of how much light slows when it travels through a material. Wavelength-dependent refraction separates visible wavelengths into colors.

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