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  2. Spectral slope - Wikipedia

    en.wikipedia.org/wiki/Spectral_slope

    In astrophysics and planetary science, spectral slope, also called spectral gradient, is a measure of dependence of the reflectance on the wavelength. In digital signal processing , it is a measure of how quickly the spectrum of an audio sound tails off towards the high frequencies, calculated using a linear regression .

  3. Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Fourier_transform

    An example application of the Fourier transform is determining the constituent pitches in a musical waveform.This image is the result of applying a constant-Q transform (a Fourier-related transform) to the waveform of a C major piano chord.

  4. Gradient - Wikipedia

    en.wikipedia.org/wiki/Gradient

    The gradient of F is then normal to the hypersurface. Similarly, an affine algebraic hypersurface may be defined by an equation F(x 1, ..., x n) = 0, where F is a polynomial. The gradient of F is zero at a singular point of the hypersurface (this is the definition of a singular point). At a non-singular point, it is a nonzero normal vector.

  5. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    A diagram of the electromagnetic spectrum, showing various properties across the range of frequencies and wavelengths. The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band.

  6. F wave - Wikipedia

    en.wikipedia.org/wiki/F_wave

    F wave persistence - measure of alpha motor neuron excitability calculated as the number of F responses elicited divided by the number of stimuli presented. The minimal F wave latency is typically 25-32 ms in the upper extremities and 45-56 ms in the lower extremities. F wave persistence is the number of F waves obtained per the number of ...

  7. Fresnel equations - Wikipedia

    en.wikipedia.org/wiki/Fresnel_equations

    The Poynting vector for a wave is a vector whose component in any direction is the irradiance (power per unit area) of that wave on a surface perpendicular to that direction. For a plane sinusoidal wave the Poynting vector is ⁠ 1 / 2 ⁠ ‍ Re{E × H ∗}, where E and H are due only to the

  8. Dispersion relation - Wikipedia

    en.wikipedia.org/wiki/Dispersion_relation

    Dispersion occurs when sinusoidal waves of different wavelengths have different propagation velocities, so that a wave packet of mixed wavelengths tends to spread out in space. The speed of a plane wave, v {\displaystyle v} , is a function of the wave's wavelength λ {\displaystyle \lambda } :

  9. Wave equation - Wikipedia

    en.wikipedia.org/wiki/Wave_equation

    The wave equation is linear in u and is left unaltered by translations in space and time. Therefore, we can generate a great variety of solutions by translating and summing spherical waves. Let φ(ξ, η, ζ) be an arbitrary function of three independent variables, and let the spherical wave form F be a delta function.