Blackbody radiation

Definition

Blackbody radiation is the thermal electromagnetic radiation emitted by an object that absorbs all incident radiation, regardless of wavelength or angle. It is characterized by a specific spectrum and intensity that depend solely on the object's temperature.

5 Must Know Facts For Your Next Test

1. The spectrum of blackbody radiation is described by Planck's law, which quantifies how much energy is emitted at different wavelengths for a given temperature.
2. Wien's displacement law states that the wavelength at which the emission of a blackbody peaks is inversely proportional to its temperature.
3. The total energy radiated per unit surface area of a blackbody across all wavelengths increases with the fourth power of the blackbody's absolute temperature (Stefan-Boltzmann law).
4. Blackbodies are idealized objects and do not exist in reality, but many physical objects approximate blackbody behavior well enough for practical purposes.
5. Understanding blackbody radiation was key to the development of quantum mechanics, as classical physics could not explain certain aspects like ultraviolet catastrophe.

Review Questions

• What law describes the peak wavelength emission of a blackbody and how does it relate to temperature?
• How does Stefan-Boltzmann law relate to blackbody radiation?
• Why was the study of blackbody radiation important in the development of quantum mechanics?

Related terms

Planck's Law:

Describes the spectral density of electromagnetic radiation emitted by a blackbody in thermal equilibrium at a given temperature.

Wien's Displacement Law:

\(\lambda_{\text{max}} T = b\), where \(\lambda_{\text{max}}\) is the peak emission wavelength, \(T\) is the absolute temperature, and \(b\) is Wien's constant.

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