# Definition:Planck's Constant

## Definition

Planck's constant is the physical constant $h$ whose value is defined as:

$h = 6 \cdotp 62607 \, 015 \times 10^{-34} \, \mathrm J \, \mathrm s$

where the units $\mathrm J \, \mathrm s$ are joule seconds.

Planck's constant defines the quantum nature of energy and relates the energy of a photon to its frequency. It is used for describing the behaviour of particles and waves at an atomic scale.

Planck's constant also occurs in Heisenberg's uncertainty principle.

Physical quantities with the same dimension include angular momentum and action.

## Also known as

Planck's constant is also seen referred to as the Planck constant.

## Source of Name

This entry was named for Max Karl Ernst Ludwig Planck.