Question

Suppose a uniform plane wave travels in an unbounded medium. We know that, as a uniform plane wave, the E and H are perpendicular to each other and also perpendicular to the direction of propagation. Are E and H always in phase? Why?

Answer 1

Yes, in a uniform plane wave traveling through an unbounded medium, the electric (E) and magnetic (B) fields are always in phase, meaning their peaks and troughs coincide, and the ratio of their magnitudes equals the speed of light.

Step-by-step explanation:

In electromagnetic waves, such as light, the electric field (E) and the magnetic field (B) are indeed always in phase when they travel through an unbounded medium. This means that the peaks and troughs of both fields occur at the same time and location throughout the wave. The reason for this is that E and B fields are both components of the same electromagnetic wave and are governed by Maxwell's equations, which describe their behavior. Additionally, the ratio of E to B field magnitudes is equal to the speed of light (c), indicating they change in synchrony. For clarity, these relationships and behaviors can be depicted in diagrams like Figure 24.7, which shows that E and B are in phase and perpendicular to both each other and to the direction of propagation.