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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:
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.