Planck's constant

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Definition
  1. Noun:
    • A fundamental physical constant: Planck's constant is the constant of proportionality that relates the energy of a single photon to its frequency. It is a cornerstone of quantum mechanics.
    • A specific numerical value: The constant has a fixed value, approximately 6.626 x 10^-34 joule-seconds (J⋅s).
Usage Examples
  • Noun:
    • The formula E = hν shows that a photon's energy (E) equals Planck's constant (h) multiplied by its frequency (ν).
    • Scientists use an extremely precise value of Planck's constant to define the kilogram.
Advanced Usage
  • In quantum theory: Planck's constant sets the scale for quantum effects. Actions or angular momentum in physical systems are quantized in units of ħ (h-bar), which is Planck's constant divided by 2π.
    • The uncertainty principle is formulated using the reduced Planck constant, ħ.
Variants and Related Words
  • Reduced Planck constant (ħ): Also called "h-bar," it is Planck's constant divided by 2π (ħ = h / 2π). This quantity appears frequently in quantum mechanical equations.
    • The Schrödinger equation uses the reduced Planck constant.
Synonyms
  • h (the standard symbol for Planck's constant).
  • Quantum of action (a historical and conceptual synonym emphasizing its role in quantization).
Related Phrases and Concepts
  • Planck's law: The law describing the electromagnetic radiation emitted by a black body in thermal equilibrium, which originally introduced the constant.
  • Planck units: A system of natural units defined using fundamental constants, including Planck's constant, the speed of light, and the gravitational constant.
Noun
  1. the constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second

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