Blackbodies

Definition

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

5 Must Know Facts For Your Next Test

1. The concept of a blackbody is crucial for understanding Planck's law and the quantization of energy.
2. A perfect blackbody in thermal equilibrium emits radiation called blackbody radiation, which has a specific spectrum described by Planck's law.
3. The peak wavelength of the emitted radiation shifts according to Wien's displacement law: $\lambda_{max} = \frac{b}{T}$, where $b$ is Wien's constant and $T$ is the temperature in Kelvin.
4. The total energy emitted per unit area by a blackbody is given by the Stefan-Boltzmann law: $E = \sigma T^4$, where $\sigma$ is the Stefan-Boltzmann constant and $T$ is the temperature in Kelvin.
5. Blackbodies played a key role in the development of quantum mechanics as they highlighted the need for quantized energy levels to explain observed spectra.

Review Questions

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:

$\lambda_{max} = \frac{b}{T}$; states that the wavelength at which the emission of a blackbody spectrum is maximized inversely varies with its absolute temperature.

Stefan-Boltzmann Law: $E = \sigma T^4$; indicates that the total energy radiated per unit surface area of a blackbody is proportional to the fourth power of its absolute temperature.