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In the physical sciences, the wavenumber (or wave number), also known as repetency, [1] is the spatial frequency of a wave. Ordinary wavenumber is defined as the number of wave cycles divided by length; it is a physical quantity with dimension of reciprocal length , expressed in SI units of cycles per metre or reciprocal metre (m −1 ).
The decimetre (SI symbol: dm) is a unit of length in the metric system equal to 10 −1 metres ( 1 / 10 m = 0.1 m). To help compare different orders of magnitude , this section lists lengths between 10 centimeters and 100 centimeters (10 −1 meter and 1 meter).
The most common form is the quarter-wave monopole, in which the antenna is approximately one quarter of the wavelength of the radio waves. It is said to be the most widely-used antenna in the world. [3] [4] Monopoles shorter than one-quarter wavelength, called electrically short monopoles are also widely used since they are more compact ...
The length of a sinusoidal wave is commonly expressed as an angle, in units of degrees (with 360° in a wavelength) or radians (with 2π radians in a wavelength). So alternately the electrical length can be expressed as an angle which is the phase shift of the wave between the ends of the conductor [1] [3] [5]
V, v 0, v m. Here v 0 is used. m s −1 [L][T] −1 (Oscillatory) acceleration amplitude A, a 0, a m. Here a 0 is used. m s −2 [L][T] −2: Spatial position Position of a point in space, not necessarily a point on the wave profile or any line of propagation d, r: m [L] Wave profile displacement
Depending on context, wave height may be defined in different ways: For a sine wave, the wave height H is twice the amplitude (i.e., the peak-to-peak amplitude): [1] =.; For a periodic wave, it is simply the difference between the maximum and minimum of the surface elevation z = η(x – c p t): [1] = {()} {()}, with c p the phase speed (or propagation speed) of the wave.
The wave vector and angular wave vector are related by a fixed constant of proportionality, 2 π radians per cycle. It is common in several fields of physics to refer to the angular wave vector simply as the wave vector, in contrast to, for example, crystallography. [1] [2] It is also common to use the symbol k for whichever is in use.
[citation needed] The loading provided by the helix allows the antenna to be physically shorter than its electrical length of a quarter-wavelength. This means that for example a 1 / 4 wave antenna at 27 MHz is 2.7 m (110 inches; 8.9 feet) long and is physically quite unsuitable for mobile applications. The reduced size of a helical ...