Inc. Fundamentals of Infrared. Convection The transfer of heat, from the heat source to the object being heated, via a fluid medium. That medium is commonly air. The transfer of heat via electromagnetic radiation between the heat source and the object to be heated.
Radiation is broken down into many subsets divided by different wavelengths.
The wavelength spectrum ranging from .72 to 1000 microns. The wavelength is inversely proportional to temperature. As the temperature goes up, the wavelength goes down. It wasn't until World War II that infrared heating came into heavy use. It speed up the production of military equipment.