In the frame of the spinor formalism of the electromagnetic field, the propagation of a plane wave in a random medium with a view to obtaining the moments of the energy density is considered. Using two different approximations to the solution of the spinor wave equation, it is shown that the energy conservation requires, on the statistics of the refractive index, some extra conditions difficult
... [Show full abstract] (eventually impossible) to satisfy. For the variance of the light intensity, a result valid for weakly scattering media is given. It is concluded that ‘‘dishonest’’ methods (in Keller’s terminology) have to be used.