## Tuesday, April 23, 2013

### Max Planck - Born in April 23, 1858

Max Karl Ernst Ludwig Planck, (April 23, 1858 – October 4, 1947) was a German theoretical physicist who originated quantum theory, which won him the Nobel Prize in Physics in 1918.
 Max Planck. Credit: Wikipedia
Planck made many contributions to theoretical physics, but his fame rests primarily on his role as originator of the quantum theory. This theory revolutionized human understanding of atomic and subatomic processes, just as Albert Einstein’s theory of relativity revolutionized the understanding of space and time. Together they constitute the fundamental theories of 20th-century physics. Both have led humanity to revise some of its most cherished philosophical beliefs, and have brought about industrial and military applications that affect many aspects of modern life.
His work on Black Body Radiation was the begging of Quantum Mechanics.

The Planck constant (denoted h, also called Planck's constant) is a physical constant that is the quantum of action in quantum mechanics. The Planck constant was first described as the proportionality constant between the energy (E) of a photon and the frequency (f) of its associated electromagnetic wave. This relation between the energy and frequency is called the Planck relationE = h f.

"Blackbody radiation" or "cavity radiation" refers to an object or system which absorbs all radiation incident upon it and re-radiates energy which is characteristic of this radiating system only, not dependent upon the type of radiation which is incident upon it. The radiated energy can be considered to be produced by standing wave or resonant modes of the cavity which is radiating.
From the assumption that the electromagnetic modes in a cavity were quantized in energy with the quantum energy equal to Planck's constant times the frequency, Planck derived a radiation formula. The average energy per "mode" or "quantum" is the energy of the quantum times the probability that it will be occupied:

This average energy times the density of such states, expressed in terms of either frequency or wavelength
gives the energy density , the Planck radiation formula.
Font: HyperPhysics, Wikipedia

Here is a simulation of the Blacbody radiation (PhET)

You can also try this cool simulation from Open Source Physics.

Finally watch this video with a brief History of Quantum Mechanics: