Definition of Planck's constant in English:

Planck's constant

(also Planck constant)


  • A fundamental constant, equal to the energy of a quantum of electromagnetic radiation divided by its frequency, with a value of 6.626 × 10⁻³⁴ joule-seconds.

    ‘The top three on most people's lists are the speed of light in a vacuum, Newton's gravitational constant, and Planck's constant, the foundation of quantum mechanics and the key to Heisenberg's infamous uncertainty principle.’
    • ‘Of course it may be that the speed of light and the charge on the electron and the gravitational constant and Planck's constant, and so on, will one day be explained as deriving from more basic realities.’
    • ‘A general expression for these reactions shows that the photon of light given off has an energy equal to Planck's constant times the frequency of the light emitted.’
    • ‘The energies of the allowed quantized vibrational states are related to Planck's constant, a quantum number v, the strength of the bond and reciprocally to the masses of the atoms involved.’
    • ‘For electromagnetism, the coupling constant is called the fine structure constant a and is formed by the electron charge, Planck's constant and the speed of light.’