Radiation refers to heat transfer that occurs across an intervening air space with no material substance involved.

• A. True
• B. False
• C. Only in vacuum
• D. Only with water heat transfer

Answer: (A)

Radiation transfers heat through electromagnetic waves and does not require a material medium to carry the energy. This means energy can move from one object to another across empty space, or through air, without relying on molecule-to-molecule contact. The intervening substance in the path (like air) doesn’t participate in the transfer; the energy travels as waves between the objects. That’s why describing radiation as heat transfer across a space with no material substance involved is accurate. The other ideas don’t fit because radiation isn’t limited to vacuum, isn’t dependent on water, and doesn’t need to rely on a material to carry the heat in the way conduction or convection do.