WordNet
n. the rate of flow of radiant energy (electromagnetic waves)
Wikipedia
In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted or received, per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of radiant flux is the watt (W), that is the joule per second in SI base units, while that of spectral flux in frequency is the watt per hertz and that of spectral flux in wavelength is the watt per metre —commonly the watt per nanometre .
Usage examples of "radiant flux".
Thus, a feature of the surface configuration that was reasonably permanent, behaved with the properties of mass, and reflected part of the radiant flux impinging on it would look like a rock.