Black Body

Planck’s Law of Radiation describes the spectral specific radiation Mλs of the black body into the half-space as a function of its temperature T and the observed wavelength λ. It thus represents the most basic relationship for non-contact temperature measurement.

The maximum of the spectral specific radiation shifts with increasing temperature to shorter wavelengths. A variety of other relationships can be derived, two of which are briefly named below.
By integrating the spectral radiation intensity over all wavelengths from zero to infinity, one obtains the value for the total radiation emitted by the body. This relationship is referred to as the → Stefan Boltzmann Law.

MλS = σ · T4 [W · m-2] mit σ = 5,67 · 10-8 [Wm-2T-4]

The total emitted radiation of a black body in the entire wavelength range increases in proportion to the fourth power of its absolute temperature.
It can be seen from the graphical representation of Planck’s Law of Radiation that the wavelength at which the emitted radiation of a black body emits the maximum shifts as the temperature changes. → Wien’s Displacement Law describes this connection and can be derived by differentiation from Planck’s equation. The wavelength at which the maximum of the radiation is located shifts with increasing temperature to the short-wave range.

λmax · T = 2898 µm · K