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  2. Wavenumber - Wikipedia

    en.wikipedia.org/wiki/Wavenumber

    For example, a wavenumber in inverse centimeters can be converted to a frequency expressed in the unit gigahertz by multiplying by 29.979 2458 cm/ns (the speed of light, in centimeters per nanosecond); [5] conversely, an electromagnetic wave at 29.9792458 GHz has a wavelength of 1 cm in free space.

  3. Free spectral range - Wikipedia

    en.wikipedia.org/wiki/Free_spectral_range

    The free spectral range of a diffraction grating is the largest wavelength range for a given order that does not overlap the same range in an adjacent order. If the ( m + 1)-th order of λ {\displaystyle \lambda } and m -th order of ( λ + Δ λ ) {\displaystyle (\lambda +\Delta \lambda )} lie at the same angle, then

  4. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    Frequencies observed in astronomy range from 2.4 × 10 23 Hz (1 GeV gamma rays) down to the local plasma frequency of the ionized interstellar medium (~1 kHz). Wavelength is inversely proportional to the wave frequency, [ 1 ] so gamma rays have very short wavelengths that are fractions of the size of atoms , whereas wavelengths on the opposite ...

  5. Visible spectrum - Wikipedia

    en.wikipedia.org/wiki/Visible_spectrum

    For example, the long-wave (red) limit changes proportionally to the position of the L-opsin. The positions are defined by the peak wavelength (wavelength of highest sensitivity), so as the L-opsin peak wavelength blue shifts by 10 nm, the long-wave limit of the visible spectrum also shifts 10 nm.

  6. Spectroradiometer - Wikipedia

    en.wikipedia.org/wiki/Spectroradiometer

    The effective wavelength (spectral) range of a spectrometer is determined not only by the grating dispersion ability but also depends on the detectors' sensitivity range. Limited by the semiconductor's band gap the silicon-based detector responds to 200-1100 nm while the InGaAs based detector is sensitive to 900-1700 nm (or out to 2500 nm with ...

  7. Wavelength - Wikipedia

    en.wikipedia.org/wiki/Wavelength

    The wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests (on top), or troughs (on bottom), or corresponding zero crossings as shown. In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats.

  8. Spectral flux density - Wikipedia

    en.wikipedia.org/wiki/Spectral_flux_density

    In this case, [1] spectral flux density is the quantity that describes the rate at which energy transferred by electromagnetic radiation is received from that unresolved point source, per unit receiving area facing the source, per unit wavelength range. At any given wavelength λ, the spectral flux density, F λ, can be determined by the ...

  9. Radiance - Wikipedia

    en.wikipedia.org/wiki/Radiance

    The latter is commonly measured in W⋅m −2 ⋅nm1. This is sometimes also confusingly called "spectral intensity". J e,λ [nb 4] watt per square metre, per metre W/m 3: M⋅L −1 ⋅T −3: Radiant exitance: M e [nb 2] watt per square metre W/m 2: M⋅T −3: Radiant flux emitted by a surface per unit area. This is the emitted component ...