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The giant galaxy around the giant black hole

On April 10, 2019, the Event Horizon Telescope (EHT) unveiled the first-ever image of a black hole's event horizon, the area beyond which light cannot escape the immense gravity of the black hole. That giant black hole, with ...

NEOWISE celebrates five years of asteroid data

NASA's Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission released its fifth year of survey data on April 11, 2019. The five years of NEOWISE data have significantly advanced scientists' knowledge of ...

Detecting pollution with a compact laser source

Researchers at EPFL have come up with a new middle infrared light source that can detect greenhouse and other gases, as well as molecules in a person's breath. The compact system, which resembles a tiny suitcase, contains ...

Image: SOHO's equinox sun

Last Wednesday, all locations on our planet enjoyed roughly the same number of hours of day and night. This event, called an equinox, takes place twice a year – around 20 March and then again around 23 September.

Energy loss gives unexpected insights in evolution of quasar

An international team of astrophysicists observed for the first time that the jet of a quasar is less powerful on long radio wavelengths than earlier predicted. This discovery gives new insights in the evolution of quasar ...

Mass manufacturing of metasurfaces

The mass production of flat optical devices with sub-wavelength structures could soon be a reality, thanks to a metasurface fabrication technique developed by researchers at A*STAR.

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Wavelength

In physics, the wavelength of a sinusoidal wave is the spatial period of the wave – the distance over which the wave's shape repeats. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves. Wavelength is commonly designated by the Greek letter lambda (λ). The concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.

Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths.

Examples of wave-like phenomena are sound waves, light, and water waves. A sound wave is a periodic variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Water waves are periodic variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary periodically in both lattice position and time.

Wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle in the water moves in a circle of the same diameter as the wave height, unrelated to wavelength.

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