2. Characteristic radiation quantities

2.1 Properties of an electromagnetic wave, spectral range

The uniformity or non-uniformity of the radiation beam and its state of coherence or incoherence will be given little consideration in this article, as these parameters will have little or no influence on the reference instruments studied. However, the effect of radiation polarization will have to be taken into account, as reference detectors are most often calibrated with polarized radiation, whereas they are used with radiation of any polarization.

On the other hand, the frequency of the radiation, most often expressed in radiometry by its wavelength, will be an essential parameter, as the response of the detectors will systematically be given as a function of this parameter. Consequently, measurements...