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.
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The concept of a blackbody is crucial for understanding Planck's law and the quantization of energy.
A perfect blackbody in thermal equilibrium emits radiation called blackbody radiation, which has a specific spectrum described by Planck's law.
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.
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.
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
What defines a perfect blackbody and how does it interact with electromagnetic radiation?
Explain how Wien's displacement law relates to blackbody radiation.
How does Planck's law describe the spectrum of radiation emitted by a blackbody?
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.