Black Body Radiation

What it's about:

With the growth of electric lighting at the end of the 19th century, electric companies turned to physicists try and extract the most light from lightbulbs, using as little energy as possible.

Max Planck was one of them, and soon discovered light could not be solely addressed as a continuous stream of energy. This was the birth of quantum physics.

Max Planck

Max Karl Ernst Ludwig Planck was born in Kiel, Germany, on April 23 1858. He studied at the Universities of Munich and Berlin, where his teachers included Kirchhoff and Helmholtz, and received his doctorate of philosophy at Munich in 1879. The Prussian Academy of Sciences appointed him Permanent Secretary in 1912.

Planck was 42 years old in 1900 when he made the famous discovery that in 1918 won him the Nobel Prize for Physics . He was also the first prominent physicist to champion Einstein’s special theory of relativity. It is not surprising that he subsequently made no discoveries of comparable importance.

Nevertheless, he continued to contribute at a high level to various branches of optics, thermodynamics and statistical mechanics, and other fields. He is one of the few scientist who stayed in Germany during the war. Planck died on October 4, 1947.

Where?

Planck's constant:

• 6.62•10^-34 J/s
  Planck's constant, describing the minimum amount of energy in a photon.
• E=hνeV
  Amount of energy in a photon depending on the frequency of the radiation.

Discovery Description:

As far as scientists knew, light intensity was only supposed to get stronger as the frequency got higher but this meant a high frequency radiation emitted unlimitted energy (Ultraviolet Catastrophe).
Max Planck, instead of thinking of light as a wave, thought of light as discreet paquets of energy (quantas). This theory implied that, in order for a body to radiate a higher frequency, it needs significantly more energy, and thus solving the Ultraviolet catastrophe. Light was thus not a continuous stream like Thomas Young had shown. It behaves like particules.

In order for a light source to emit in a certain wavelength, the quanta must first contain enough energy to vibrate at that particular frequency. The higher the wavelength, the more energy is needed.

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