An electromagnetic wave that is visible to the human eye, characterized by its wavelength and frequency.Light is an electromagnetic wave that is visible to the human eye, spanning wavelengths from about 380 to 750 nanometers. It is a self-propagating oscillation of electric and magnetic fields that travels at the speed of light in a vacuum (299,792,458 meters per second). Light exhibits both wave-like and particle-like properties, described by quantum mechanics as photons. Its wavelength determines its perceived color, from violet at short wavelengths to red at long ones, and its frequency is directly related to its energy.
The wave theory of light was established by Christiaan Huygens in the 17th century and refined by Thomas Young's double-slit experiment in 1801. James Clerk Maxwell unified electricity and magnetism in the 1860s, showing that light is an electromagnetic wave. The quantum nature was introduced by Max Planck in 1900 and Albert Einstein in 1905 with the photon concept.
Light is produced when charged particles, typically electrons, transition between energy levels in atoms or oscillate in a material. The wave propagates as a transverse oscillation of the electromagnetic field, with the electric and magnetic components perpendicular to each other and to the direction of travel. When light interacts with matter, it can be absorbed, reflected, refracted, or scattered, depending on the material's properties and the light's wavelength. The wave nature explains phenomena like interference and diffraction, while the particle nature explains the photoelectric effect and the discrete energy of photons.
Light is fundamental to technologies such as fiber-optic communications, lasers, photography, solar cells, and optical microscopy, as well as to our basic sense of vision.
The speed of light is so fundamental that it defines the meter — the meter is now officially defined as the distance light travels in a vacuum in 1/299,792,458 of a second.
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