of: electromagnetic radiation, often produced from a continuous emission spectrum (e.g. a source of white light) which has been passed through a specified absorbing medium.
is: the distribution of (relative) spectral brightness with respect to frequency or wavelength. [P8.2]
may be displayed: as a graph of the (relative) spectral brightness plotted against wavelength or frequency, or (photographically) as a band of varying levels of brightness and darkness. [P8.2]
may exhibit: (especially for a gas, a vapour or a plasma) characteristic absorption lines, in which case it is often referred to as an absorption line spectrum, or (especially in the case of a solid or a liquid) smoothly varying absorption across a broad range of frequencies or wavelengths. [P8.2]
Copyright 1997, The Open University