  In this work the interaction of electromagnetic field with quasi-periodic
media has been scrutinized. We have obtained the formula for a distorted medium
polarizability tenzor in the X-ray frequency band. Also there have been
obtained the X-rays dynamic diffraction equations for media with arbitrary
smooth distortion. For these equations the Takagi-Tuipin equations are obtained
as a particular case. We have got a very simple formula for the coefficient of
X-ray reflaction on the bent Bragg mirror. We have scrutinized the example of
calculating the X-rays reflaction and focusing by the bent Bragg mirror. Also
in this work one could find the rezults of calculating the reflected X-rays
caustics form. It is shown that there exists a possibility of linear dimensions
of the X-rays focusing area having typical values of 10^-7 cm.
