Which statement best describes a ground wave?

• A. It travels along the Earth's surface at low frequencies.
• B. It travels through space and avoids the atmosphere.
• C. It bounces off the ionosphere at high frequencies.
• D. It is only used for weather radar.

Answer: (A)

Ground waves travel along the Earth’s surface, guided by the conductivity of the ground and the atmosphere near it. Because of these interactions, longer wavelengths at lower frequencies can hug the surface and follow the planet’s curvature, making ground-wave propagation strongest in the low-frequency range. This is why the description that a ground wave travels along the Earth’s surface at low frequencies is the best fit.

It’s not space-based; that would be propagation through space. It doesn’t rely on bouncing off the ionosphere, which is how skywave works at higher frequencies. And ground waves aren’t the mode used for weather radar, which operates with microwave frequencies and line-of-sight paths.