In radar reflectivity order, which material has the highest reflectivity?

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

Answer: (A)

Radar reflectivity comes from how strongly a material can reflect an incident electromagnetic wave, which depends mainly on conductivity and magnetic properties at the surface. Metals that conduct electricity well create a large boundary impedance difference with air, causing most of the energy to bounce back. Steel stands out because, as a ferrous metal, it has higher magnetic permeability in many radar frequency ranges in addition to good conductivity, which increases the impedance contrast at the surface and boosts the reflected signal. Aluminum is also a strong reflector due to its conductivity, but its lower magnetic permeability means it doesn’t reach the same level of reflection as steel in the same conditions. Wood and concrete are nonmetals with much lower conductivity and no magnetic enhancement, so their reflections are comparatively weak.