Which of the following processes does NOT require a medium to transfer heat? *
A conduction
B radiation
C convection
The correct answer and explanation is :
Correct Answer: B. Radiation
Explanation:
Heat can be transferred from one object or substance to another through three primary mechanisms: conduction, convection, and radiation. Each of these has different requirements and behaviors.
- Conduction is the transfer of heat through direct contact between molecules. This process occurs mainly in solids, where molecules are tightly packed. When one part of a solid object is heated, its molecules vibrate faster and transfer energy to neighboring molecules. For example, when you heat one end of a metal rod, the other end eventually becomes hot due to conduction. A medium is absolutely necessary for conduction to take place—specifically, particles must be physically touching.
- Convection involves the transfer of heat by the movement of fluids—liquids or gases. When part of a fluid is heated, it becomes less dense and rises, while cooler, denser fluid sinks. This movement creates convection currents that help transfer heat. Boiling water is a good example: hot water rises and cooler water moves down to replace it. Convection also requires a medium, typically a fluid, to facilitate this circulation.
- Radiation, on the other hand, is the emission of energy as electromagnetic waves—typically infrared radiation. The most important aspect of radiation is that it does not require a medium to transfer heat. This is why the Sun’s heat can reach Earth through the vacuum of space. Unlike conduction and convection, radiation can travel through empty space, making it unique.
In summary, while conduction and convection both require a physical medium for heat transfer, radiation does not. It can occur across the vacuum of space, which is why it is the primary method by which solar energy reaches Earth. This fundamental difference is what makes option B: Radiation the correct answer.