Blackbody Radiation: Structures & Vocabulary

A blackbody is an idealized object that absorbs incident radiation perfectly and emits a continuous spectrum determined only by its temperature. Real stars are not perfect blackbodies, but their broad continua often resemble blackbody curves closely enough to make the model extremely useful.

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.

Planck's law gives spectral radiance at every wavelength. Wien's displacement law states that peak wavelength is inversely proportional to temperature, while the Stefan-Boltzmann law says total surface flux rises as T^4. These are different statements: moving the peak and increasing integrated power are related consequences of the same thermal spectrum, but one should not substitute one law for the other.