Which form of heat transfer can occur through empty space and does not require a medium?

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

Answer: (C)

Heat can travel in different ways, but through empty space only radiation works. Radiation is the transfer of energy by electromagnetic waves, so it doesn’t need particles to move energy from one place to another. That’s why sunlight reaches Earth across the vacuum of space and why you can feel warmth from a fire or the Sun without anything touching it. Conduction and convection both rely on matter: conduction needs direct contact and particle interactions, convection requires a moving fluid to carry heat, and osmosis is about solvent movement across a membrane driven by concentration differences, not heat transfer. So the form that can operate in empty space without a medium is radiation.