Stefan-Boltzmann law of radiation

Definition

The Stefan-Boltzmann law of radiation states that the total energy radiated per unit surface area of a black body is directly proportional to the fourth power of the black body's absolute temperature. Mathematically, it is expressed as $E = \sigma T^4$, where $E$ is the energy radiated, $\sigma$ is the Stefan-Boltzmann constant, and $T$ is the absolute temperature.

5 Must Know Facts For Your Next Test

1. The Stefan-Boltzmann constant ($\sigma$) has a value of approximately $5.67 \times 10^{-8} \text{W/m}^2\text{K}^4$.
2. The law applies specifically to idealized black bodies, which are perfect emitters and absorbers of radiation.
3. Real objects can be approximated by multiplying with an emissivity factor ($\epsilon$), ranging from 0 to 1.
4. The law helps explain why hotter objects emit more radiation across all wavelengths than cooler ones.
5. It forms the basis for understanding thermal radiation and heat transfer in various physical systems.

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Related terms

Black Body: An idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.

Emissivity:

A measure of an object's ability to emit infrared energy compared to an ideal black body, ranging from 0 (no emission) to 1 (perfect emitter).

Thermal Radiation:

Electromagnetic radiation generated by the thermal motion of particles in matter, which includes infrared radiation emitted by objects due to their temperature.