Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Planck’s constant ($h$) is a fundamental constant that relates the energy of a photon to its frequency. It has a value of approximately $6.626 \times 10^{-34}$ Js.
5 Must Know Facts For Your Next Test
Planck’s constant is integral to the equation $E = hf$, where $E$ is energy, $h$ is Planck's constant, and $f$ is frequency.
It was introduced by Max Planck in 1900 as part of his solution to the black-body radiation problem.
Planck's constant plays a crucial role in quantum mechanics, helping to describe the quantization of energy levels.
The value of Planck's constant is approximately $6.626 \times 10^{-34}$ Joule seconds (Js).
It is also used in Heisenberg's uncertainty principle, which states that the position and momentum of a particle cannot both be precisely determined simultaneously.
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Related terms
Photon: A quantum of light or other electromagnetic radiation carrying energy proportional to its frequency.
Black-body Radiation: The emission of electromagnetic radiation by an idealized object which absorbs all incident radiation, regardless of frequency or angle.
Quantization: The concept that energy can exist only in discrete levels rather than any value.