What are ground waves?

Ground waves are specifically defined as radio waves that propagate along the surface of the Earth. This mode of transmission occurs due to the interaction between the radio waves and the ground, allowing them to follow the curvature of the Earth, especially at low frequencies. Ground waves are particularly effective for communication over short to medium distances, as they can penetrate obstacles and follow the terrain.

In contrast, options that involve radio waves reflected off the ionosphere, high frequency waves, or those that travel in space describe different propagation methods. For instance, radio waves reflected off the ionosphere typically pertain to skywave propagation, which is different from ground wave propagation that relies on direct contact with the Earth’s surface. Similarly, high-frequency radio waves often deal with skywave and line-of-sight communications rather than ground wave phenomena. Thus, the correct definition of ground waves revolves around their capability to travel along the Earth's surface.