In radar reflectivity order, which material is second highest reflectivity?

• A. Masonry
• B. Concrete
• C. Aluminum
• D. Steel

Answer: (C)

Radar reflectivity, or how strongly a material returns radar energy, is dominated by how well the material supports induced currents and how its electromagnetic properties differ from air. Metals are the strongest reflectors because a radar wave induces surface currents that reradiate energy back toward the radar. Among metals, steel usually produces the strongest return due to its combination of high conductivity and magnetic permeability. Aluminum also reflects strongly because of its high electrical conductivity, but it is non-magnetic, so its return is typically a bit weaker than steel’s at radar frequencies. Non-metallic materials like concrete and masonry have much lower reflectivity on average, since they don’t support conductive surface currents as effectively unless moisture is present. Therefore, the material with the second-highest radar reflectivity in this list is aluminum.