Thermal radiation does not require any medium for energy transfer.
It is generated by the thermal motion of charged particles in matter, and therefore any material with a temperature above absolute zero gives off some radiant energy. The term thermal radiation is frequently used to distinguish this form of electromagnetic radiation from other forms, such as radio waves, x-rays, or gamma rays. Thermal radiation is electromagnetic radiation in the infra-red region of the electromagnetic spectrum, although some of it is in the visible region. It can be expressed by the following equation: Radiation heat transfer rate, q, from a body (e.g., a black body) to its surroundings is proportional to the fourth power of the absolute temperature. Thermal radiation is electromagnetic radiation in the infra-red region of the electromagnetic spectrum, although some are in the visible region.