Planck's Constant Definition

Planck's constant relates a photon's energy to its frequency.
Planck's constant relates a photon's energy to its frequency. Aeriform / Getty Images

Planck's Constant Definition: Planck's constant is the proportionality constant relating a photon's energy to its frequency.

Planck's constant is expressed by the symbol h

h = 6.62606896(33) x 10-34 J·sec
h = 4.13566733(10) x 10−15 eV·sec