Radiation is heat transfer by which means?

• A. Heat transfer through a fluid.
• B. Transfer of energy by electromagnetic waves, can travel through a vacuum.
• C. Heat transfer by direct contact between objects.
• D. Heat transfer through conduction in a solid.

Answer: (B)

Radiation is heat transfer by electromagnetic waves, which can travel through a vacuum. This means energy can move from a hot object to its surroundings even without any matter present—like the Sun warming Earth through empty space. The other forms of heat transfer involve matter: direct contact transfers energy by particle interactions (conduction), and energy moving with a flowing fluid carries heat (convection). Descriptions that reference a fluid or conduction in a solid describe those other mechanisms, not radiation. That’s why the electromagnetic-wave description is the best fit.