Which type of wave travels directly from the transmitting antenna to the receiving antenna?

The direct wave refers to the type of wave that travels in a straight line from the transmitting antenna to the receiving antenna without any interference or reflection from other surfaces. This direct path allows for strong, clear communication signals, especially in line-of-sight conditions.

When a signal is transmitted, a direct wave is the most efficient in reaching its destination, as it avoids obstacles and any potential distortions that could occur from reflections or scattering. In contrast, ground-reflected waves (which bounce off the ground) or scattered waves (which result from interactions with various objects) can introduce delays or multi-path effects, potentially degrading the quality of the signal. Surface waves are another type of propagation that can follow the curvature of the earth but are not as direct as the straight path offered by the direct wave. Thus, the correct answer highlights the most straightforward and effective mode of transmission between antennas.