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In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. [ 1 ] [ 2 ] In other words, it is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings .
Tuning dial on 1946 Dynatron Merlin T.69 console radio receiver, showing LW wavelengths between 800 and 2000 metres (375–150 kHz). In radio, longwave, long wave or long-wave, [1] and commonly abbreviated LW, [2] refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band.
Longer-wavelength radiation such as visible light is nonionizing; the photons do not have sufficient energy to ionize atoms. Throughout most of the electromagnetic spectrum, spectroscopy can be used to separate waves of different frequencies, so that the intensity of the radiation can be measured as a function of frequency or wavelength ...
A monochromatic wave (a wave of a single frequency) consists of successive troughs and crests, and the distance between two adjacent crests or troughs is called the wavelength. Waves of the electromagnetic spectrum vary in size, from very long radio waves longer than a continent to very short gamma rays smaller than atom nuclei.
The wavelength is the distance from one peak (crest) of the wave's electric field to the next, and is inversely proportional to the frequency of the wave. The relation of frequency and wavelength in a radio wave traveling in vacuum or air is = , where
The equation says the matter wave frequency in vacuum varies with wavenumber (= /) in the non-relativistic approximation. The variation has two parts: a constant part due to the de Broglie frequency of the rest mass ( ℏ ω 0 = m 0 c 2 {\displaystyle \hbar \omega _{0}=m_{0}c^{2}} ) and a quadratic part due to kinetic energy.
In physics, coherence length is the propagation distance over which a coherent wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Wave interference is strong when the paths taken by all of the interfering waves differ by less than the coherence length. A wave with a longer coherence length is closer to a perfect ...
The 41.8% point is the wavelength-frequency-neutral peak (i.e. the peak in power per unit change in logarithm of wavelength or frequency). These are the points at which the respective Planck-law functions 1 / λ 5 , ν 3 and ν 2 / λ 2 , respectively, divided by exp ( hν / k B T ) − 1 attain their maxima.