Which describes radiation?

• A. The transfer of energy with the help of electromagnetic waves
• B. The movement of heat through a liquid
• C. The conduction through a metal rod
• D. The rotation of molecules to generate heat

Answer: (A)

Radiation is the transfer of energy through electromagnetic waves, so energy can move through space or air without needing a medium. This is why you can feel the warmth of the sun or a campfire even when you’re not touching them. Other heat transfer methods require matter: conduction happens through direct contact in a solid, like heat moving along a metal rod; convection involves the bulk movement of a fluid, such as warm air rising or heated water circulating. The idea of energy being produced by rotating molecules describes heat generation, not how heat travels from one object to another. So the description that matches radiation is energy transfer via electromagnetic waves.