Velocity perturbation ratio of the transmitted wave in the x-direction with respect to the incoming wave, , as a function of the incidence angle, θ_I, for different density contrasts, ρ_c. The vertical dashed and dashed-dotted lines denote the Critical angle, θ_C, and the Brewster angle, θ_B, for the different density contrasts. The horizontal blue dashed line shows that the intersection of the velocity perturbation and the Brewster angle is equal to one for all different density contrasts.