Two infinite planes separated by a distance l carry a uniform surface charge of densities and =

Two infinite planes separated by a distance l carry a uniform surface charge of densities σ and = σ (Fig. 3.7). The planes have round coaxial holes of radius R, with l << R. Taking the origin O and the x coordinate axis as shown in the figure, find the potential of the electric field and the projection of its strength vector Ex on the axes of the system as functions of the x coordinate. Draw the approximate plot φ (x).