Definitions for "Action spectrum"
A description of the wavelength dependence of effects introduced by electromagnetic radiation on biological matter. For example, a sunburn action spectrum describes the degree to which varying wavelengths of ultraviolet rays inflict sunburn. It is usually displayed as a function on a graph.
the efficiency with which electromagnetic radiation produces a photochemical reaction plotted as a function of the wavelength of the radiation
a graph of the reciprocal of the radiant exposure required to produce the given effect at each wavelength