Stefan–Boltzmann law

In quantum physics, the Stefan-Boltzmann law (sometimes called Stefan's Law) states that the black-body radiation energy emitted by a given object is directly proportional to the temperature of the object raised to the fourth power. The equation for this law is:

R=σT⁴

where σ is the Stefan-Boltzmann constant, which is equal to 5.670 373(21) x 10^-8 W m^-2 K^-4, and where R is the energy radiated per unit surface area and per unit time. T is temperature, which is measured in Kelvin scale. Although this law is accurate and helpful, it is only usable for the energy radiated by blackbodies.

Stefan–Boltzmann Law Media

• 

  Total emitted energy, j \equiv M^{\circ}, of a black body as a function of its temperature, T. The upper (black) curve depicts the Stefan–Boltzmann law, M^{\circ} = \sigma\,T^4. The lower (blue) curve is total energy according to the Wien approximation, M^{\circ}_{W} = M^{\circ} / \zeta(4) \approx 0.924 \, \sigma T^{4} \!\,

• 

  Log–log graphs of peak emission wavelength and radiant exitance vs. black-body temperature. Red arrows show that 5780 K black bodies have 501 nm peak and 63.3 MW/m2 radiant exitance.

• 

  Deriving the Stefan–Boltzmann Law using Planck's law.