In radio propagation, which path travels along the surface of the earth?

In radio propagation, which path travels along the surface of the earth?

• A. Through the ionosphere
• B. In free space
• C. Along the surface of the earth
• D. Within optical fiber

Answer: (C)

Ground wave propagation travels along the Earth's surface. This path occurs when radio waves stay close to the ground, guided by the boundary between the earth and the air. At lower frequencies, part of the wave couples with the ground and follows the terrain, bending with the planet as it travels, which is why long-distance communications at these frequencies rely on this surface-hugging behavior. The other options describe waves that either go through the ionosphere (skywave and reflection off ionized layers), travel in a straight line through space (line-of-sight in free space), or stay inside a fiber (optical communication), none of which match the wave staying along the surface.

Ground wave propagation travels along the Earth's surface. This path occurs when radio waves stay close to the ground, guided by the boundary between the earth and the air. At lower frequencies, part of the wave couples with the ground and follows the terrain, bending with the planet as it travels, which is why long-distance communications at these frequencies rely on this surface-hugging behavior. The other options describe waves that either go through the ionosphere (skywave and reflection off ionized layers), travel in a straight line through space (line-of-sight in free space), or stay inside a fiber (optical communication), none of which match the wave staying along the surface.