<P> The Stefan--Boltzmann constant (also Stefan's constant), a physical constant denoted by the Greek letter σ (sigma), is the constant of proportionality in the Stefan--Boltzmann law: "the total intensity radiated over all wavelengths increases as the temperature increases", of a black body which is proportional to the fourth power of the thermodynamic temperature . The theory of thermal radiation lays down the theory of quantum mechanics, by using physics to relate to molecular, atomic and sub-atomic levels . Slovenian physicist Josef Stefan formulated the constant in 1879, and it was later derived in 1884 by Austrian physicist Ludwig Boltzmann . The equation can also be derived from Planck's law, by integrating over all wavelengths at a given temperature, which will represent a small flat black body box . "The amount of thermal radiation emitted increases rapidly and the principal frequency of the radiation becomes higher with increasing temperatures". The Stefan--Boltzmann constant can be used to measure the amount of heat that is emitted by a blackbody, which absorbs all of the radiant energy that hits it, and will emit all the radiant energy . Furthermore, the Stefan--Boltzmann constant allows for temperature (K) to be converted to units for intensity (W m), which is power per unit area . </P> <P> The value of the Stefan--Boltzmann constant is given in SI units by </P>

Does stefan's constant depend upon wavelength of radiation