Which statement about radiation is true?

Which statement about radiation is true?

• A. Heat is moved through the environment by direct contact.
• B. Heat is moved by circulating a liquid or gas.
• C. Heat is transferred mainly by conduction through solids.
• D. Heat is moved through space by electromagnetic waves and does not require contact.

Answer: (D)

Radiation is the transfer of heat energy through electromagnetic waves. Unlike conduction, which requires direct contact and collisions of particles, or convection, which moves heat with the flow of a circulating liquid or gas, radiation does not need a medium at all. This is why heat from the Sun reaches Earth through the vacuum of space—the energy travels as electromagnetic waves and can be absorbed by objects without any surrounding matter. All objects emit some electromagnetic radiation based on their temperature, and hotter objects emit more energy. The other statements describe conduction through solids or convection via fluids, which are not the radiative mechanism.

Radiation is the transfer of heat energy through electromagnetic waves. Unlike conduction, which requires direct contact and collisions of particles, or convection, which moves heat with the flow of a circulating liquid or gas, radiation does not need a medium at all. This is why heat from the Sun reaches Earth through the vacuum of space—the energy travels as electromagnetic waves and can be absorbed by objects without any surrounding matter. All objects emit some electromagnetic radiation based on their temperature, and hotter objects emit more energy. The other statements describe conduction through solids or convection via fluids, which are not the radiative mechanism.