Heat transfer in the form of invisible electromagnetic waves is called:

The correct answer is radiation. In the context of heat transfer, radiation refers specifically to the transfer of heat in the form of electromagnetic waves, which can travel through a vacuum as well as through air or other mediums. This process does not require any physical contact between objects, which distinguishes it from conduction and convection.

Conduction involves the transfer of heat through direct contact between materials, where thermal energy moves from the hotter object to the cooler one at the molecular level. Convection relates to the transfer of heat through fluids (liquids or gases) where warmer, less dense areas rise while cooler, denser areas sink, establishing a flow that carries heat with it.

Emission is a broader term that can refer to any release of energy, including electromagnetic radiation, but it does not specifically denote the transfer of heat through electromagnetic waves as radiation does. Thus, radiation is the most precise answer to the question about the transfer of heat through invisible electromagnetic waves.