At distances of a few wavelengths, the E and H fields transition into which region?

• A. Near Fields
• B. Far Fields
• C. Transitional Fields
• D. Radiating Zone

Answer: (B)

The main idea is that space around an antenna is divided into regions where the field behavior changes. At distances of a few wavelengths, the reactive, energy-storing parts of the near field have diminished, and the radiated field dominates. In this far-field region, the electric and magnetic fields are perpendicular to each other and to the direction of propagation, they oscillate in phase, and their amplitudes fall off roughly as 1/r. This lets the wave be treated as a propagating plane wave, which is why the far-field description is the best fit. Near-field would still involve complex E and H relationships and energy storage close to the source, which isn’t the case here.