The thicker the film, the greater the amplitude of the electric field strength of an electromagnetic wave reflected from a conductive film. The figure shows a typical dependence of the reflected wave amplitude on the film thickness. At the initial moment (in the region x < x₁), the amplitude linearly depends on the film thickness x, then the linear dependence is broken, and in the region x > x₂, the amplitude of the reflected wave differs little from the amplitude of the incident wave E₀. Explain this dependency.