This article explores the problems of convergence of iterative methods for solving nonlinear inverse problems of wave tomography, namely, two-coefficient inverse problems of reconstruction of unknown velocity and absorption coefficients at the second and first time derivatives of the scalar wave function, respectively. To solve a nonlinear problem, the Multi-Stage method is employed, the essence of which is that at the first stages of the method only the low-frequency part of the signals is used. Estimation of the low-frequency band is the central issue of the method. In this work, an expression is obtained for scattering on inhomogeneities, which, for given values of the problem parameters, allows us to estimate the limit of the low-frequency band for the first stage of the method. This expression for scattering was obtained in the Born wave approximation in two dimensions under the assumption that the wavelength is small compared to the size of the inhomogeneity. It is shown that the resulting expression for wave scattering by an inhomogeneity is in complete agreement with heuristic estimates of the initial frequency obtained in the ray approximation. Using the obtained expression, scattering effects on inhomogeneities in velocity and absorption are compared. This study explains the reason for the better reconstruction of the velocity function compared to that of absorption in the inverse problem. Model calculations on a supercomputer confirmed the correctness of the obtained estimates and theoretical results.