Definition

1. Noun:
   • (Physics) Planck's radiation law: A fundamental equation in quantum mechanics and thermodynamics that describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature. It marks the birth of quantum theory.

Usage

• Noun:
  • Planck's radiation law accurately predicts the intensity of radiation at different wavelengths for a black body.
  • The derivation of Planck's radiation law resolved the ultraviolet catastrophe problem in classical physics.

Advanced Usage

• "to derive Planck's radiation law": To mathematically obtain the law from first principles, typically involving quantum statistical mechanics.
  • Max Planck originally derived Planck's radiation law by introducing the concept of energy quanta.
• "consistent with Planck's radiation law": Describing experimental data or a theoretical model that agrees with the predictions of the law.
  • The cosmic microwave background radiation spectrum is remarkably consistent with Planck's radiation law for a black body at 2.7 Kelvin.

Variants and Related Words

• Planck's law (n): A common abbreviated name for Planck's radiation law.
  • Planck's law is a cornerstone of modern physics.
• Black-body radiation (n): The type of electromagnetic radiation described by Planck's radiation law.
  • The study of black-body radiation led directly to the formulation of Planck's radiation law.
• Spectral radiance (n): The quantity described by Planck's radiation law.
  • Planck's radiation law gives the spectral radiance as a function of wavelength and temperature.

Synonyms

• Planck's law: The most direct synonym.
• Black-body radiation formula: A descriptive synonym emphasizing its application.

Related Phrases

• To obey Planck's radiation law: For a physical system's emission to follow the law's predictions.
  • A perfect black body will precisely obey Planck's radiation law.
• The limit of Planck's radiation law: Referring to its behavior in classical (Rayleigh-Jeans) or high-energy (Wien's approximation) limits.
  • At long wavelengths, Planck's radiation law reduces to the Rayleigh-Jeans law.

Noun

1. (physics) an equation that expresses the distribution of energy in the radiated spectrum of an ideal black body