Which statement about radiation is true?

Which statement about radiation is true?

• A. There must be a difference in temperature between energy source and target area.
• B. Direct contact between energy source and target area is required.
• C. The rate is not influenced by the energy source size.
• D. A medium is required to transmit radiation energy.

Answer: (A)

Radiation transfers heat through electromagnetic waves and can occur through empty space, so no medium is required. The amount of radiant energy that actually transfers depends on a temperature difference between the source and the target; without that difference, there is no net transfer. This is why the statement about a temperature difference being necessary is true. Radiation does not require direct contact, unlike conduction, and the rate of transfer does depend on factors like the size of the emitting surface, distance, and emissive properties, so saying the rate is unaffected by source size isn’t correct.

Radiation transfers heat through electromagnetic waves and can occur through empty space, so no medium is required. The amount of radiant energy that actually transfers depends on a temperature difference between the source and the target; without that difference, there is no net transfer. This is why the statement about a temperature difference being necessary is true. Radiation does not require direct contact, unlike conduction, and the rate of transfer does depend on factors like the size of the emitting surface, distance, and emissive properties, so saying the rate is unaffected by source size isn’t correct.