Planck's constant (redirected from Planck constant)

Planck's constant (plängks), fundamental constant of the quantum theory. It is represented by the letter h and has a value of 6.63 × 10⁻³⁴ J-sec. The combination h/2π, denoted by h (called "h-bar"), occurs frequently.

---

Planck's constant [′pläŋks ‚kän·stənt]

(quantum mechanics)

A fundamental physical constant, the elementary quantum of action; the ratio of the energy of a photon to its frequency, it is equal to 6.62606876 ± 0.00000052 × 10^-34joule-second. Symbolizedh. Also known as quantum of action.

---

Planck's constant

A fundamental physical constant which represents the elementary quantum of action, action being defined as energy multiplied by time. Introduced by Max Planck in 1900, it has the value h = 6.6261 × 10^-27 erg-second or 6.6261 × 10^-34 joule-second. The symbol ℏ, sometimes called the Dirac h, is often used for convenience in physics to denote the quantity h/2π, where π = 3.1416….

As used by Planck in deriving his radiation law, h multiplied by the frequency of radiation represented a bundle of energy, that is, a quantum of energy. Radiant energy at any wavelength can occur only as multiples of this energy; thus energy is quantized. See Compton effect, Fundamental constants, Heat radiation, Quantum mechanics