Resulting field from a superposition

Let us consider a zone in space where two waves co-exist. For all points in this space, the resulting electromagnetic field is simply equal to the sum of the fields:

The observer, whether it be the naked eye or the detector, is sensitive to the square module of the electromagnetic field, i.e. . However, it must be taken into account that the field oscillates at a frequency of the order of 1014 Hz and that currently, even the best detectors cannot “see” phenomena that happen faster than 1012 Hz. Consequently, the signal observed is a statistical average of , i.e.[2]:

where means statistical average.