Peculiarities of propagation of point sourse radiation through layer of absorbing random medium

At recent years there were find out some peculiarities of changes of angular spectrum of wave power with distance in random inhomogeneous medium, caused by strong dissipation [ 1,2]. They can be observed in such important for practical applications cases as light propagation in ocean, infrared light in clouds and near infrared light in biological tissues. The report is dewouted to investigations of peculiarities of angular spectrum of power of point source radiation, when the source is elevated above the layer of absorbing random medium. The results can be applied in development of new methods of remote sensing. Let us describe flat layer of absorbing random inhomogeneous medium of thickness Z by complex permitivity. Then we consider that deviations of the permitivity from the mean value are small and the inhomogeneties have a large scale. Suppose that medium above and below the layer is nonabsorbing and homogeneous . Denote the distances from the layer to the point source and receiver (below the layer) by LI and L2 respectively. The angular spectrum of scattered wavefield we investigate in small angle approximation. In the case of strong phase fluctuations the spectrum has gaussian shape. In this case shift of maximum and width squared of spatial spectrum of power are determined by derivatives of correlation hnction of phase fluctuations. After rather bulky calculations there can be derived expressions for the shift of maximum and width squared of the spatial spectrum. The expressions were analyzed both analytically and numerically for power spectrum of fluctuations. As the result we derived that in the case of small distances from the source and receiver to the layer of' turbid medium ( Z/Li>5, Z/L2>5 ) width of the angular wave power spectrum does not depend on absorption and is equal to the width calculated for point source in anabsorbing medium. Shift of the maximum in this case tends to zero [3]. Vice versa in the case of Z/L1<2 the width and shift of the maximum begin anomalously quick increase with the growing of imaginary part of the layer permitivity . When Z/Li tends to zero, the expressions agree with results of works [ 21 It should be noted that under condition Z/Li=const the increasing of distance L2 from receiver to the layer causes decreasing of the width and changing of sign of the shift of maximum of the angular spectrum.