  Studied experimentally the origin of the non-zero reflection of p-polarized
radiation (TM) of Brewster's angle. The results have shown the residual
reflected light in the vicinity of Brewster angle occurs due to inaccessibility
100% polarization degree the incident linearly-polarized radiation and
installation of the zero azimuthal angle. These factors create the s-component
of the radiation reflected from the examined surface indeed. A smooth change of
reflected light polarization in the vicinity of Brewster angle in the sequence
p-s-p appears due to the changing power proportion of reflected p-, and
s-components but not is the result of the atomically thin transitional layer at
the border of the material/environment according to Drude model. Metrological
aspects of refractive index measurement by Brewster angle are investigated: due
to the above-mentioned factors, as well as due to the contribution of the
reflected scattered light caused by on residual roughness of the optical
surface. Advantages of Brewster refractometry for any materials and films
without restrictions on the topology of samples and their light scattering and
absorption are demonstrated
