Planck's Constant -- from Eric Weisstein's World of Physics

Planck's Constant

The fundamental constant of nature

(1)

arising in quantum mechanical problems. The quantity , called h-bar or sometimes the reduced Planck constant, is also commonly encountered. For example, the energy of a photon with frequency is given in terms of h by

(2)

Similarly, the Planck law for blackbody radiation is

(3)

where T is the temperature, c is the speed of light, and k is Boltzmann's constant. h also arises in the Schrödinger equation.

h-Bar, Photon

References

NIST. "NIST Fundamental Physical Constants." http://physics.nist.gov/cgi-bin/cuu/Value?h.

Planck, M. "Zur Theorie des Gesetzes der Energieverteilung im Normalspektrum." Verhandl. Deutsch. phys. Ges. 2, 237, 1900.

Planck, M, "Über das Gesetz der Energieverteilung in Normalspektrum." Ann. Physik 4, 553, 1901.