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Centre Wavelength
The centre wavelength is the power-weighted mean wavelength: : \lambda_\text = \frac \int p(\lambda) \lambda\, d\lambda, and the total power is : P_\text = \int p(\lambda) \,d\lambda, where p(\lambda) is the power spectral density, for example in W/nm. The above integrals theoretically extend over the entire spectrum, however, it is usually sufficient to perform the integral over the spectrum where the spectral density p(\lambda) is higher than a fraction of its maximum. See also * Dominant wavelength In color science, the dominant wavelength is a method of characterizing a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. A color's dominant wavelength is the wavelength of monochromatic spectral light that evok ... References Waves {{optics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weighted Mean
The weighted arithmetic mean is similar to an ordinary arithmetic mean (the most common type of average), except that instead of each of the data points contributing equally to the final average, some data points contribute more than others. The notion of weighted mean plays a role in descriptive statistics and also occurs in a more general form in several other areas of mathematics. If all the weights are equal, then the weighted mean is the same as the arithmetic mean. While weighted means generally behave in a similar fashion to arithmetic means, they do have a few counterintuitive properties, as captured for instance in Simpson's paradox. Examples Basic example Given two school with 20 students, one with 30 test grades in each class as follows: :Morning class = :Afternoon class = The mean for the morning class is 80 and the mean of the afternoon class is 90. The unweighted mean of the two means is 85. However, this does not account for the difference in number of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter ''lambda'' (λ). 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 of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. Wavelength depends on the medium (for example, vacuum, air, or water) that a wav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Density
The power spectrum S_(f) of a time series x(t) describes the distribution of power into frequency components composing that signal. According to Fourier analysis, any physical signal can be decomposed into a number of discrete frequencies, or a spectrum of frequencies over a continuous range. The statistical average of a certain signal or sort of signal (including noise) as analyzed in terms of its frequency content, is called its spectrum. When the energy of the signal is concentrated around a finite time interval, especially if its total energy is finite, one may compute the energy spectral density. More commonly used is the power spectral density (or simply power spectrum), which applies to signals existing over ''all'' time, or over a time period large enough (especially in relation to the duration of a measurement) that it could as well have been over an infinite time interval. The power spectral density (PSD) then refers to the spectral energy distribution that would be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peak Wavelength
Peak or The Peak may refer to: Basic meanings Geology * Mountain peak ** Pyramidal peak, a mountaintop that has been sculpted by erosion to form a point Mathematics * Peak hour or rush hour, in traffic congestion * Peak (geometry), an (''n''-3)-dimensional element of a polytope * Peak electricity demand or peak usage * Peak-to-peak, the highest (or sometimes the highest and lowest) points on a varying waveform * Peak (pharmacology), the time at which a drug reaches its maximum plasma concentration * Peak experience, psychological term for a euphoric mental state Resource production In terms of resource production, the peak is the moment when the production of a resource reaches a maximum level, after which it declines; in particular see: * Peak oil * Peak car * Peak coal * Peak copper * Peak farmland * Peak gas * Peak gold * Peak minerals * Peak phosphorus * Peak uranium * Peak water * Peak wheat * Peak wood Other basic meanings * Visor, a part of a hat, known as a "peak" in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dominant Wavelength
In color science, the dominant wavelength is a method of characterizing a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. A color's dominant wavelength is the wavelength of monochromatic spectral light that evokes an identical perception of hue. Determination Helmholtz coordinates The Helmholtz Coordinates are a Polar coordinate system for defining a 2D chromaticity plane. The circumferential coordinate is the dominant wavelength, which is analogous to hue of the HSL and HSV color spaces. The radial coordinate is the purity, which is analogous to saturation of the HSL and HSV color spaces. Color space Any chromaticity diagram from any color space can be used for calculating the dominant wavelength as long as it is bound by a spectral locus defined by wavelength. However, the values will change depending on which color space is used. Unless otherwise stated, the CIE 1931 color space (CIEXYZ) is used., but the CIELUV color space is sometimes used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
