Noun
English Wikipedia has an article on:radiometryWikipedia
radiometry (usually uncountable, plural radiometries)
(physics) The branch of science that deals with the detection and measurement of radiant electromagnetic energy.
In radiometry and colorimetry (or color science more generally), the spectral power distribution (SPD) of a light source is a measure of the power contributed by each frequency or color in a light source. Source: Internet
SURF III now serves as the U.S. national standard for source-based radiometry throughout the generalized optical spectrum. Source: Internet