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Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. [3] [4] The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ). For a modulated wave, wavelength may refer to the carrier wavelength of the signal.
For example, a wavenumber in inverse centimeters can be converted to a frequency expressed in the unit gigahertz by multiplying by 29.979 2458 cm/ns (the speed of light, in centimeters per nanosecond); [5] conversely, an electromagnetic wave at 29.9792458 GHz has a wavelength of 1 cm in free space.
The SI unit of spatial frequency is the reciprocal metre (m −1), [1] although cycles per meter (c/m) is also common. In image-processing applications, spatial frequency is often expressed in units of cycles per millimeter (c/mm) or also line pairs per millimeter (LP/mm). In wave propagation, the spatial frequency is also known as wavenumber.
Phase comparison is a comparison of the phase of two waveforms, usually of the same nominal frequency. In time and frequency, the purpose of a phase comparison is generally to determine the frequency offset (difference between signal cycles) with respect to a reference. [3]
The phase velocity is given in terms of the wavelength λ (lambda) and time period T as v p = λ T . {\displaystyle v_{\mathrm {p} }={\frac {\lambda }{T}}.} Equivalently, in terms of the wave's angular frequency ω , which specifies angular change per unit of time, and wavenumber (or angular wave number) k , which represent the angular change ...
In practice N is set to 1 cycle and t = T = time period for 1 cycle, to obtain the more useful relation: = / Hz = s −1 [T] −1: Angular frequency/ pulsatance ω = = / Hz = s −1 [T] −1: Oscillatory velocity v, v t, v: Longitudinal waves:
where the angular frequency is the temporal component, and the wavenumber vector is the spatial component. Alternately, the wavenumber k can be written as the angular frequency ω divided by the phase-velocity v p, or in terms of inverse period T and inverse wavelength λ.
In frequency (and thus energy), UV rays sit between the violet end of the visible spectrum and the X-ray range. The UV wavelength spectrum ranges from 399 nm to 10 nm and is divided into 3 sections: UVA, UVB, and UVC. UV is the lowest energy range energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions.