Which term best describes heat transfer through electromagnetic waves from a warmer object to a cooler one?

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

Answer: (C)

Heat transfer by electromagnetic waves from a warmer object to a cooler one is radiation. This means energy travels as electromagnetic waves—think infrared light among others—without needing any physical contact or a surrounding fluid. The warming effect you feel from a fire or the Sun warming the Earth is radiation because the energy is moving through space or air as waves, not by touching molecules or by moving air itself. The hotter the object and the greater its surface area and emissivity, the more energy it radiates, following principles like the Stefan-Boltzmann relationship.

Conduction would require direct contact between substances, with energy passed through molecular interactions. Convection involves the bulk movement of a fluid, carrying heat as the fluid cycles. Evaporation isn’t a mode of heat transfer itself; it’s a phase-change process that can accompany heating, but it doesn’t describe how heat travels from one object to another.