Which heat loss mechanism involves heat transfer to the surroundings via radiation?

• A. Convection
• B. Radiation
• C. Conduction
• D. Evaporation

Answer: (B)

Radiation is the transfer of heat by electromagnetic waves from a warmer surface to cooler surroundings. It doesn’t require contact or a moving fluid, so heat can be lost even in still air or a vacuum. The warm body emits infrared energy, and the surrounding environment absorbs some of that energy, producing heat loss proportional to factors like the body's surface area and the temperature difference with the surroundings. This is why you can feel heat loss near a cold window or from a sun-warmed skin surface in a cooler room, even without touching anything or having air flow. Other mechanisms involve direct contact with a surface (conduction), movement of air or liquid (convection), or a phase-change process like evaporation, which are distinct from radiation.