Physical Sciences

Quantum Mechanics

1900

Intermediate

Planck's Equation

E = h\nu

Energy of a photon is proportional to its frequency—light comes in discrete packets.

By Max Planck

Physical Sciences

Planck's Equation

1900 · Max Planck

Human Reviewed

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Why it matters: Birth of quantum mechanics; enabled lasers, solar cells, and spectroscopy.

Discoverers: Max Planck (1900)

What does it mean?

Energy of a photon is proportional to its frequency—light comes in discrete packets.

Why should I care?

Birth of quantum mechanics; enabled lasers, solar cells, and spectroscopy.

Equation Compass

North — Prerequisites

West — History

Max Planck

East — Applications

South — Derivations

Derivation

Variables & Units

Symbol	Name	Unit	Meaning
$E$	Energy	J	Photon energy
$h$	Planck constant	—	6.626×10⁻³⁴ J·s
$ν$	Frequency	Hz	Electromagnetic frequency

Worked Example

Green light (550 nm): ν = c/λ, E = hν ≈ 3.6×10⁻¹⁹ J.

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ℏ ν

Sources & further reading

Search Wikipedia Search Wolfram MathWorld Open in Wolfram|Alpha Watch explainers on YouTube

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