Blackbody Radiation: Foundations

A blackbody spectrum has a smooth distribution with a temperature-dependent peak. Wien's law links temperature to the wavelength of maximum emission, while the Stefan-Boltzmann law says emitted power per unit area grows as the fourth power of absolute temperature.

Thermal motion in matter produces a distribution of electromagnetic emission. Raising temperature increases the total emitted energy and shifts the peak toward shorter wavelengths because higher-energy modes become more strongly populated.

Laboratory cavities approximate blackbodies, and stellar spectra show temperature-dependent continuum shapes. The Sun's photospheric continuum corresponds roughly to a temperature near 5800 K even though absorption lines are superimposed.

A blackbody is an idealized thermal emitter whose spectral shape depends only on temperature. Real stars are not perfect blackbodies, but their continua often approximate the model well enough to define effective temperature. Hotter blackbodies emit more energy per unit area and peak at shorter wavelengths, linking color and luminosity to physical temperature through quantitative laws rather than subjective appearance.