Transcript: All atoms or molecules are in constant motion or vibration. The emission or radiation that results is called thermal radiation. Thermal radiation is directly related to the temperature of a substance, and it has a peak wavelength of the emission or characteristic wavelength given by Wien’s law. By contrast, non thermal radiation has no characteristic wavelength. The radiation extends over a large frequency range in what’s called a power law, and non thermal radiation does not correspond to an equilibrium physical process. Non thermal radiation can be observed at all wavelengths from radio to gamma rays.