Field and Wave Electromagnetics 2nd Edition by David Cheng

Exercise 20

Justify the statement that the steady-current problem associated with a conductor buried in a poorly conducting medium near a plane boundary with air, as shown in Fig. 1 can be replaced by that of the conductor and its image, both immersed in the poorly conducting medium as shown in Fig. 2.
Figure: Steady-current problem with a plane boundary
Figure 1: Conductor in a poorly conducting medium near a plane boundary.

Figure 2: Image conductor in conducting medium replacing the plane boundary.