Planck constant

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The Planck constant (denoted as h) is a fundamental physical constant that is central to quantum mechanics. It describes the size of the discrete units, or quanta, of energy that are involved in quantum phenomena. The Planck constant is named after the German physicist Max Planck, who first introduced it in 1900.

Definition and Value

The Planck constant is defined as exactly 6.62607015×10⁻³⁴ J·s. This definition was adopted by the SI in 2019, based on the fixed numerical value of the constant.

Significance in Quantum Mechanics

The Planck constant is crucial in the field of quantum mechanics. It appears in the Heisenberg uncertainty principle, which states that the position and momentum of a particle cannot both be precisely determined at the same time. The constant also features in the Schrödinger equation, which describes how the quantum state of a physical system changes over time.

Planck's Relation

Planck's relation links the energy (E) of a photon to its frequency (ν) through the equation:

E = hν

This relation is fundamental in the study of quantum optics and photonics.

Reduced Planck Constant

The reduced Planck constant, also known as h-bar (ℏ), is defined as:

ℏ = h / 2π

It is commonly used in quantum mechanics and appears in the Dirac equation and quantum field theory.

Applications

The Planck constant is used in various applications, including:

• Quantum computing
• Spectroscopy
• Photovoltaics
• Quantum cryptography

See Also

• Max Planck
• Quantum mechanics
• Heisenberg uncertainty principle
• Schrödinger equation
• Photon
• Quantum optics
• Dirac equation
• Quantum field theory

Related Pages

• Physical constant
• International System of Units
• Quantum computing
• Spectroscopy
• Photovoltaics
• Quantum cryptography