of incident and reflected waves, interference occurs. Following the process used in equation (5.1.7), the computed total wave is partly traveling wave along the y‐axis, while along the negative x‐axis, it is partly standing wave. However, the minima of the standing wave do not reach zero levels as Γ⊥ ≠ − 1, like a PEC. Although, the wave is traveling along the interface in the y‐direction, still the wave is not the surface wave, as in the x‐direction the field is not confined to the surface. Under certain conditions, discussed in subsection (5.3.2), propagation of the surface wave is possible. The surface wave is further discussed in section (7.5) of chapter 7.
The Oblique Incidence on a Perfect Electric Conductor
If the medium #2 is a PEC, i.e. η2 = 0, εr2 = ∞, the reflection coefficient is
In equation (5.2.11a, b, c) harmonic‐time dependence ejωt is suppressed. It is seen from equations (5.2.11a, b, c) that the interference produces a total wavefield moving in the y‐direction along the interface, while along the direction of the normal, i.e. in the x‐direction, it is a standing wave. It shows that the interference field pattern is traveling along the interface.
5.2.2 TM (Parallel) Polarization Case
Figure (5.3a) shows an oblique incidence of TMz‐polarized plane wave ray at the interface of two electrically different media. The electric field of the incident wave is in the (x‐y)‐ plane of incidence, so the incident wave has a parallel polarization as the Einc field is parallel to the plane of incidence. The parallel polarization, or p‐polarization, is also known as the transverse magnetic (TM) polarization as the z‐oriented magnetic field is normal to the plane of incidence. It is also called π‐polarization.
The visual inspection of the direction of field vectors in Fig (5.3a) shows that the magnetic field component Hz is normal to the (x − y)‐plane, i.e. to the plane of polarization, while the electric field components Ex and Ey are in the plane of polarization. The field components of the incident, reflected, and transmitted (refracted) TM‐polarized obliquely incident wave, as shown in Fig (5.3a), are summarized below:
(5.2.13)
Transmitted wave:
The continuity of the tangential electric and magnetic field components, across the interface at x = 0, provides the following expression:
The Poynting vectors are the same as that of the TE‐polarization. The phase matching, from equation (5.2.15), again provides Snell's reflection and refractions laws as given by equation (5.2.7). However, the amplitude matching provides different expressions for the reflection (ΓllTM), and transmission τllTM coefficients of the parallel polarized obliquely incident plane wave:
Figure 5.3 Oblique incidence of a plane wave with TM‐polarization at the interface of two media.
For normal incidence, equations (5.2.16c,d) reduce to equations (5.1.3a,b). Equations (5.2.16c,d) are known as the Fresnel's Equations of the TM‐polarized waves. It is noted that
Medium #1
The total field is a summation of the incident and reflected fields:
Medium #2
In medium #1, there is a traveling wave along the y‐axis, whereas, in the direction of normal to the interface, the wave is a standing wave. However, the minima of the standing wave never reach zero levels as
The Oblique Incidence on a Perfect Electric Conductor
If medium #2 is a perfect conductor,
