What is the physical mechanism that begins radiation heat transfer?

• A. Conduction
• B. Emission and Absorption
• C. Convection
• D. Evaporation

Answer: (B)

Radiation heat transfer starts with an object emitting electromagnetic energy because of its temperature. Those photons travel away and can be absorbed by another body, converting that radiant energy into heat. This emission and subsequent absorption are the processes that enable heat to move through space or air without needing a medium. Conduction requires direct contact between materials, and convection relies on the bulk motion of a fluid, while evaporation is a phase-change process involving latent heat. The amount emitted (and thus transferred) depends on temperature and material properties like emissivity.