# Definition:Planck's Constant

## Definition

Planck's constant is the physical constant $h$ which defines the quantum nature of energy and relates the energy of a photon to its frequency.

Thus:

$E = \dfrac h f$

where:

$E$ denotes the energy of a photon
$f$ denotes the frequency of that photon
$h$ denotes Planck's constant.

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.

### Value

 $\ds h$ $=$ $\ds 6 \cdotp 62607 \, 015 \times 10^{-34}$ joule seconds $\quad$ This sequence is A003676 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008). $\ds$ $=$ $\ds 6 \cdotp 62607 \, 015 \times 10^{-27}$ erg seconds

### Symbol

$h$

The symbol for Planck's constant is $h$.

The $\LaTeX$ code for $h$ is h .

### Dimension

Planck's constant has the dimension $\mathsf {M L^2 T^{-1} }$.

### Units

The SI unit for Planck's constant is given as joule seconds:

$\mathrm {J \, s}$

## 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.