How does thermal radiation differ from conduction and convection?

Thermal radiation differs from conduction and convection as it doesn't require a medium to transfer heat energy.

Thermal radiation, conduction, and convection are the three methods of heat transfer. However, they operate differently. Conduction and convection require a medium, such as a solid, liquid, or gas, to transfer heat. On the other hand, thermal radiation can transfer heat energy through the vacuum of space, which makes it unique.

Conduction is the process of heat transfer between substances in direct contact. It occurs when faster-moving particles collide with slower ones, transferring kinetic energy. This is common in solids, where particles are closely packed and can easily interact. For instance, when you heat one end of a metal rod, the heat travels to the cooler end through conduction.

Convection, meanwhile, is the heat transfer in fluids (liquids and gases) due to the movement of particles. When a fluid is heated, it expands, becomes less dense, and rises. The cooler, denser fluid then sinks, creating a convection current that circulates heat throughout the fluid. This is why water in a pot starts to circulate when heated.

Thermal radiation is fundamentally different. It is the emission of electromagnetic waves, particularly infrared waves, from a heated object. These waves can travel through a vacuum, like space, and transfer energy. When these waves hit an object, they can be absorbed, heating the object. This is how the Sun's energy reaches Earth. Unlike conduction and convection, thermal radiation doesn't require particles to transfer heat, making it the only method of heat transfer that can work in a vacuum.

In summary, while conduction and convection rely on particle interaction to transfer heat, thermal radiation uses electromagnetic waves, enabling heat transfer without a medium.