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  2. Spectrum (physical sciences) - Wikipedia

    en.wikipedia.org/wiki/Spectrum_(physical_sciences)

    In the physical sciences, the spectrum of a physical quantity (such as energy) may be called continuous if it is non-zero over the whole spectrum domain (such as frequency or wavelength) or discrete if it attains non-zero values only in a discrete set over the independent variable, with band gaps between pairs of spectral bands or spectral ...

  3. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    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. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and ...

  4. Spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Spectroscopy

    Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of astronomy, chemistry, materials science, and physics, allowing the composition, physical structure and electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over astronomical distances.

  5. Spectrum analyzer - Wikipedia

    en.wikipedia.org/wiki/Spectrum_analyzer

    The frequency halfway between the stop and start frequencies on a spectrum analyzer display is known as the center frequency. This is the frequency that is in the middle of the display's frequency axis.

  6. Redshift - Wikipedia

    en.wikipedia.org/wiki/Redshift

    Redshifts cannot be calculated by looking at unidentified features whose rest-frame frequency is unknown, or with a spectrum that is featureless or white noise (random fluctuations in a spectrum). [20] Redshift (and blueshift) may be characterized by the relative difference between the observed and emitted wavelengths (or frequency) of an object.

  7. Spectral analysis - Wikipedia

    en.wikipedia.org/wiki/Spectral_analysis

    Spectrum analyzer, a hardware device that measures the magnitude of an input signal versus frequency within the full frequency range of the instrument Spectral theory , in mathematics, a theory that extends eigenvalues and eigenvectors to linear operators on Hilbert space, and more generally to the elements of a Banach algebra

  8. Spectrometer - Wikipedia

    en.wikipedia.org/wiki/Spectrometer

    An XPS spectrometer. A spectrometer (/ s p ɛ k ˈ t r ɒ m ɪ t ər /) is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the spectral components are somehow mixed.

  9. Spectral band - Wikipedia

    en.wikipedia.org/wiki/Spectral_band

    Most often, it refers to electromagnetic bands, regions of the electromagnetic spectrum. [1] More generally, spectral bands may also be means in the spectra of other types of signals, e.g., noise spectrum. A frequency band is an interval in the frequency domain, limited by a lower frequency and an