Blackbody

Definition

A blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. It also emits radiation in a characteristic continuous spectrum that depends solely on the body's temperature.

5 Must Know Facts For Your Next Test

1. A blackbody is a perfect emitter and absorber of radiation.
2. The spectrum of a blackbody's emitted radiation is called blackbody radiation and follows Planck's law.
3. The peak wavelength of the emitted radiation shifts to shorter wavelengths as the temperature increases, according to Wien's displacement law.
4. The total energy emitted per unit surface area of a blackbody is proportional to the fourth power of its temperature, as described by the Stefan-Boltzmann law.
5. Real objects approximate blackbody behavior but do not perfectly match it; they are often described by their emissivity.

Review Questions

• What distinguishes a blackbody from other types of bodies in terms of radiation absorption and emission?
• How does Wien's displacement law relate to the temperature of a blackbody?
• What does the Stefan-Boltzmann law state about the relationship between temperature and total emitted energy?

Related terms

Planck's Law: Describes the spectral density of electromagnetic radiation emitted by a blackbody in thermal equilibrium at a given temperature as a function of wavelength.

Wien's Displacement Law: States that the wavelength at which the emission of a blackbody spectrum is maximized is inversely proportional to its absolute temperature.

Stefan-Boltzmann Law: $$E = \sigma T^4$$, where $E$ is the total energy radiated per unit surface area, $\sigma$ is the Stefan-Boltzmann constant, and $T$ is the absolute temperature.