41 - Radiation

A body at any temperature above absolute zero emits thermal radiation.

Energy transport by radiation does not require an intervening medium between the hot and cold surfaces. If the hot object is separated from the cold one by vacuum, heat transfer between these objects is only through radiation (as heat transfer by conduction or convection is not possible).

Radiation from a body at temperature \(T\) is considered to be emitted at all wavelengths from \(\lambda=0\) to \(\lambda=\infty\). At temperatures encountered in most engineering applications, the bulk of the thermal energy emitted lies in the wavalength between 0.1 and 100 \(\mu\)m, and this range of wavelength is generally referred to as the thermal radiation.