Definition

Noun: 1. A fundamental law of quantum mechanics: Planck's law states that electromagnetic energy is emitted or absorbed in discrete, indivisible packets called quanta (or photons), rather than as a continuous wave. The energy (E) of a single quantum is directly proportional to the frequency (ν) of the radiation: E = hν, where h is Planck's constant. 2. Specifically for blackbody radiation: More narrowly, Planck's law refers to the mathematical formula that describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature. This formula resolved the ultraviolet catastrophe problem in classical physics.

Usage Examples

• General Principle: Planck's law introduced the revolutionary concept that energy is quantized.
• Historical Context: The formulation of Planck's law marked the birth of quantum theory.
• Scientific Application: To calculate the energy of a photon of blue light, one must apply Planck's law.

Advanced Usage

• "Derive Planck's law": To mathematically obtain the formula from fundamental principles of quantum statistics and electromagnetism.
  • In advanced thermodynamics, students learn to derive Planck's law for blackbody radiation.
• "In accordance with Planck's law": Behaving or calculated in a way that follows this fundamental principle.
  • The photoelectric effect operates in accordance with Planck's law.

Variants and Related Words

• Planck constant (h) (n): The fundamental physical constant (approximately 6.626 × 10⁻³⁴ J·s) appearing in the formula of Planck's law, representing the proportionality factor between the energy of a photon and its frequency.
• Planck's radiation law (n): A full synonym, often used specifically for the blackbody radiation formula.
• Quantization (n): The core concept introduced by Planck's law, meaning that a physical quantity can have only certain discrete values.

Synonyms

• Planck radiation law
• Law of energy quantization (descriptive synonym for the general principle)

Related Phrases

• To obey/follow Planck's law: Used to describe a physical process that is consistent with this law.
  • The emission spectrum of the hot gas was found to obey Planck's law.
• A consequence of Planck's law: A result or phenomenon that stems from this law.
  • The existence of a photon is a direct consequence of Planck's law.

Noun

1. (physics) the basis of quantum theory; the energy of electromagnetic waves is contained in indivisible quanta that have to be radiated or absorbed as a whole; the magnitude is proportional to frequency where the constant of proportionality is given by Planck's constant