Light is electromagnetic energy with a wavelength that is observable to the eye or, in a technical or scientific context, the word is sometimes used to mean electromagnetic emission of all wavelengths. The elementary element that defines light is the photon. The three basic properties of lights are Intensity, or alternatively amplitude, which is related to the observation of brightness of the light, Frequency, or alternatively wavelength, perceived by humans as the color of the light, and Polarization, which is only weakly perceptible by humans under ordinary circumstances. Due to its wave–particle duality, light can show properties of both waves and particles. The study of light, known as optics, is an important research area in modern physics.
The first successful quantity of the speed of light in Europe using an earthbound apparatus was carried out by Hippolyte Fizeau in 1849. Fizeau aimed at a beam of light at a mirror several thousand metres away, and placed a rotating cog wheel in the path of the beam from the source to the mirror and back again. At a certain rate of rotary motion, the beam could pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Fizeau calculated the speed of light as 313 000 km/sv
The first successful quantity of the speed of light in Europe using an earthbound apparatus was carried out by Hippolyte Fizeau in 1849. Fizeau aimed at a beam of light at a mirror several thousand metres away, and placed a rotating cog wheel in the path of the beam from the source to the mirror and back again. At a certain rate of rotary motion, the beam could pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Fizeau calculated the speed of light as 313 000 km/sv
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