Which term corresponds to the radar propagation phenomenon where the beam bends downward due to a temperature gradient?

• A. SERRATED RANGE RINGS
• B. Sub Refraction
• C. Water in the Waveguide
• D. Elevated Ducting

Answer: (B)

The main idea is atmospheric refraction: the radar beam doesn’t travel straight because the air’s refractive index changes with height as temperature varies. A temperature gradient near the surface can bend the beam downward toward the Earth. When that downward bending occurs but isn’t strong enough to trap the wave, this condition is described as sub refraction. The other options describe different propagation effects: serrated range rings are a display artifact from irregular propagation, water in the waveguide isn’t an atmospheric path and relates to a different hardware context, and elevated ducting refers to a strong, trapping layer that channels the beam within a duct, producing much more pronounced bending.