What sort of medium does radiation heat transfer require?

• A. A solid medium
• B. A fluid medium
• C. No medium (radiation can occur in vacuum)
• D. A dense gas

Answer: (C)

Radiation heat transfer happens through electromagnetic waves that carry energy from a hotter body to a cooler one, and these waves can travel through empty space. Because no material is needed to transmit the energy, it can occur in a vacuum, like sunlight reaching Earth from the Sun.

A medium like a solid, liquid, or gas isn’t required for the transfer itself, though such materials can absorb, reflect, or transmit the radiant energy. So even without any matter present, radiant heat can occur, which is why this method is distinct from conduction or convection, both of which need a material medium to move heat.