a measure of the efficiency of radiation of a given wavelength in producing a visual sensation. It is equal to the ratio of the radiant flux at a standard wavelength to that at the given wavelength when the standard wavelength is chosen so that the maximum value of this ratio is unity ((for photopic vision)) V(λ), ((for scotopic vision)) V′(λ)
adjective 1. of or relating to a specter; ghostly; phantom. 2. resembling or suggesting a specter. 3. of, relating to, or produced by a spectrum or spectra. 4. resembling or suggesting a spectrum or spectra. adjective 1. of or like a spectre 2. of or relating to a spectrum: spectral colours 3. (physics) (of a […]
noun, Physics. 1. a series of lines in the spectrum of light emitted by excited atoms of an element, each line being related to the others in the series by a simple numerical equation and identified with a particular energy level of an atom of the element.
noun, Astronomy. 1. a category for classifying a star, as A star or G star, according to features of its spectrum, as its shape as a function of temperature and wavelength and its absorption spectrum, that indicate the surface temperature of the star and the presence of particular atoms or molecules in its outer layers: […]
noun 1. a vivid yellow color.