Plancks constant

In physics, Planck's constant, named after the physicist Max Planck, is a fundamental value equal to:

  h = 6.6261 x 10-34 Js 

appearing in all the equations of quantum mechanics. It can be seen as a conversion factor between frequency and energy, especially for photons. Sometimes the abbreviation

  h_bar = h / 2π

is used, where π is Archimedes' constant, the ratio of the circumference of a circle to its diameter.

see also: Electromagnetic radiation, Schrödinger's equation, Heisenberg's uncertainty principle, Wave-Particle duality