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S. Persheyev, D.A. Rogatkin
82
ISSN 1812-3368. Вестник МГТУ им. Н.Э. Баумана. Сер. Естественные науки. 2017. № 5
the specific electrical conductivity of the medium, so the case of
=
0 is the case of
the perfect dielectric medium. Substitution Eq. (8) into Eq. (6) gives
0
0
0
2
2
0
( , )
.
nx j
t
x
E x t E e
e
(9)
As we see, the real amplitude of the field is decreasing as the exponential function
0
2 exp
x
inside all non-perfect dielectric media when
0. This result follows
from fundamentals of the electromagnetic theory and has nothing to do with the
phenomenology approach (Eqs. (1) and (2)). However, surprisingly, it gives the same
result at
0
0
4 2 ,
K
k
where
k
0
is the wave number in a free space. Therefore, we
have an accurate understanding of the nature of light absorption and its description in
the phenomenological photometry. However, what about the scattering?
In basic Maxwell's electrodynamics, there is not such a special property of media
as the scattering coefficient. Scattering of light as the process of dispersion of the
radiation in different directions occurs with the appearance of inhomogeneities inside
the medium and (or) of boundaries between media with different
n*
. In the simplest
case of a plane boundary, when a beam of light crosses the boundary line between two
different media with different refractive index, reflection and refraction of the beam
can be observed. Which fraction of the beam is reflected and which one is refracted
(transmitted), as well as directions for both the reflection and refraction are described
well by known Fresnel equations and Snell's law. For example, a fraction of the
incident beam that is reflected from the plane boundary is given by the reflectivity
R
(
R
1). At the normal incidence
2 2
2 2
( 1)
.
( 1)
n R
n
(10)
In the common case,
R
is a function of
, i. e.,
R
=
R
(
) due to both
n
=
n
(
)
and
=
(
). Once again we see the connection with the electromagnetic properties of the
medium, in this case through the complex refractive index
n
*, but the conception of
scattering is absent yet. It is absent in the basic diffraction theory, as well. Although,
F. Grimaldi was first who carefully observed the effect of diffraction of light, and who
also coined the term diffraction, from the Latin
diffringere
, exactly 'to break into
pieces', referring to light breaking up into different directions, in electrodynamics this
phenomenon is not described as scattering, so it does not need to involve the
scattering coefficient. It just describes a light intensity as a function of ''scattering''
angle at light beam diffraction on an obstacle or on a slit when the dimension of them
is roughly comparable to the wavelength. It can correspond to a phase function in
LT&ST, but not more. The item of scattering appears in electrodynamics at
introduction of a rough boundary surface [2, 3] or at consideration of mutual optical