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  2. Spectral efficiency - Wikipedia

    en.wikipedia.org/wiki/Spectral_efficiency

    Link spectral efficiency. The link spectral efficiency of a digital communication system is measured in bit/s/Hz, or, less frequently but unambiguously, in (bit/s)/Hz.It is the net bit rate (useful information rate excluding error-correcting codes) or maximum throughput divided by the bandwidth in hertz of a communication channel or a data link.

  3. Stellar classification - Wikipedia

    en.wikipedia.org/wiki/Stellar_classification

    This system was developed through the analysis of spectra on photographic plates, which could convert light emanated from stars into a readable spectrum. Mount Wilson classes. A luminosity classification known as the Mount Wilson system was used to distinguish between stars of different luminosities.

  4. Spectral density - Wikipedia

    en.wikipedia.org/wiki/Spectral_density

    The spectral density of a fluorescent light as a function of optical wavelength shows peaks at atomic transitions, indicated by the numbered arrows. The voice waveform over time (left) has a broad audio power spectrum (right). In signal processing, the power spectrum of a continuous time signal describes the distribution of power into frequency ...

  5. Spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Spectroscopy

    Introduction. Spectroscopy is a branch of science concerned with the spectra of electromagnetic radiation as a function of its wavelength or frequency measured by spectrographic equipment, and other techniques, in order to obtain information concerning the structure and properties of matter. [4] Spectral measurement devices are referred to as ...

  6. Raman spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Raman_spectroscopy

    Raman spectroscopy. Energy-level diagram showing the states involved in Raman spectra. Raman spectroscopy ( / ˈrɑːmən /) (named after physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. [1]

  7. Spectrum (physical sciences) - Wikipedia

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

    In the physical sciences, the term spectrum was introduced first into optics by Isaac Newton in the 17th century, referring to the range of colors observed when white light was dispersed through a prism. [1] [2] Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral ...

  8. Fraunhofer lines - Wikipedia

    en.wikipedia.org/wiki/Fraunhofer_lines

    The Fraunhofer lines are typical spectral absorption lines. Absorption lines are narrow regions of decreased intensity in a spectrum, which are the result of photons being absorbed as light passes from the source to the detector. In the Sun, Fraunhofer lines are a result of gas in the Sun's atmosphere and outer photosphere.

  9. Spectral Database for Organic Compounds - Wikipedia

    en.wikipedia.org/wiki/Spectral_Database_for...

    The Spectral Database for Organic Compounds ( SDBS) is a free online searchable database hosted by the National Institute of Advanced Industrial Science and Technology (AIST) in Japan, that contains spectral data for ca 34,000 organic molecules. [1] The database is available in English and in Japanese and it includes six types of spectra: laser ...