CWNA

Answer - D - The RF phenomenon where the wave bends as it passes through a medium of different density is refraction.

Key Takeaway: Refraction describes the bending of a radio wave as it passes through a medium of different density and a constant velocity. It is similar to visible light bending as it passes from air into water. As the wave enters the dense layer of electrically charged ions, the part of the wave that enters the new medium first travels faster than the parts of the wave that have not yet entered the new medium. This abrupt increase in velocity of the upper part of the wave causes the wave to bend back toward the Earth. This bending, or change of direction, is always toward the medium that has the lower velocity of propagation.