This day in history December 14, 2019-Plancks law
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Started by metmike - Dec. 14, 2019, 10:11 p.m.

Read, learn and remember history. Pick out a good one.


https://en.wikipedia.org/wiki/December_14


1900Quantum mechanics: Max Planck presents a theoretical derivation of his black-body radiation law.


1964American Civil Rights Movement: Heart of Atlanta Motel v. United States: The Supreme Court of the United States rules that Congress can use the Constitution's Commerce Clause to fight discrimination.

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By metmike - Dec. 14, 2019, 10:14 p.m.
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Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T, when there is no net flow of matter or energy between the body and its environment.[1]

At the end of the 19th century, physicists were unable to explain why the observed spectrum of black body radiation, which by then had been accurately measured, diverged significantly at higher frequencies from that predicted by existing theories. In 1900, Max Planck heuristically derived a formula for the observed spectrum by assuming that a hypothetical electrically charged oscillator in a cavity that contained black-body radiation could only change its energy in a minimal increment, E, that was proportional to the frequency of its associated electromagnetic wave. This resolved the problem of the ultraviolet catastrophe predicted by classical physics.  This discovery was a pioneering insight of modern physics and is of fundamental importance to quantum theory.

The law

 

Planck's law accurately describes black-body radiation. Shown here are a family of curves for different temperatures. The classical (black) curve diverges from observed intensity at high frequencies.

Every physical body spontaneously and continuously emits electromagnetic radiation and the spectral radiance of a body, Bν, describes the amount of energy it emits at different radiation frequencies. It is the power emitted per unit area of the body, per unit solid angle of emission, per unit frequency.