What is a ground (or surface) wave?

What is a ground (or surface) wave?

• A. A wave that follows the curvature of the Earth and travels very long distances.
• B. A wave that travels in a straight line and does not follow the Earth's surface.
• C. A wave that bounces off the ionosphere and returns to Earth.
• D. An ideal reference wave.

Answer: (A)

Ground waves propagate by staying close to and following the Earth's surface, bending with the terrain and the curvature of the planet. This surface-guided behavior lets the energy travel far beyond the line of sight, especially at lower frequencies where the wave can couple with the ground and diffract around obstacles. That description matches a wave that travels along the surface and covers very long distances, so it’s the best fit. The other ideas describe different propagation modes: a straight-line path is typical of space or line-of-sight waves that don’t hug the ground; a wave that bounces off the ionosphere and returns to Earth is ionospheric skywave, not a ground-attached mode; and an ideal reference wave isn’t about how a signal propagates at all.

Ground waves propagate by staying close to and following the Earth's surface, bending with the terrain and the curvature of the planet. This surface-guided behavior lets the energy travel far beyond the line of sight, especially at lower frequencies where the wave can couple with the ground and diffract around obstacles. That description matches a wave that travels along the surface and covers very long distances, so it’s the best fit.

The other ideas describe different propagation modes: a straight-line path is typical of space or line-of-sight waves that don’t hug the ground; a wave that bounces off the ionosphere and returns to Earth is ionospheric skywave, not a ground-attached mode; and an ideal reference wave isn’t about how a signal propagates at all.