Which description best defines radiation?

Which description best defines radiation?

• A. Heat transfer due to direct contact via molecular agitation within a material
• B. Heat transfer due to the motion of a fluid; like circulation
• C. Heat transfer via electromagnetic radiation
• D. Heat transfer through cooling of a gas

Answer: (C)

Radiation is heat transfer by electromagnetic waves. This energy can move through empty space, so a hot object can warm another object without touching or relying on a moving fluid. Conduction requires direct contact and transfers energy through molecular interactions in solids (and through liquids in some cases), while convection involves the bulk movement of a fluid carrying heat with it. The description about cooling a gas doesn’t define a heat-transfer mechanism. So radiation, defined by energy transfer via EM waves, best fits.

Radiation is heat transfer by electromagnetic waves. This energy can move through empty space, so a hot object can warm another object without touching or relying on a moving fluid. Conduction requires direct contact and transfers energy through molecular interactions in solids (and through liquids in some cases), while convection involves the bulk movement of a fluid carrying heat with it. The description about cooling a gas doesn’t define a heat-transfer mechanism. So radiation, defined by energy transfer via EM waves, best fits.