All About Light All About Light Main Page  Classical  Relativistic  Quantum 



On the previous page, I started to discuss light from the quantum point of view. Max Planck was asked on his exam to explain the blackbody radiation spectrum. (Nobody on Earth had been able to answer this question.)
Planck came up with a crazy idea. He suggested that electromagnetic energy is emitted and absorbed in the form of discrete bundles, or "QUANTA." He stated that the energy of each quantum depends only on the frequency of the radiation, and is given by a very simple formula: The constant of proportionality h is called Planck's constant and its value is h=6.626 075 5x10^34 Js The quanta, which came to be known as PHOTONS, behave like PARTICLES! This is what made the idea so crazy: he tried to describe an electromagnetic WAVE as a PARTICLE. The notion seemed to be nonsense. Why? Please proceed to the next page, to see that these two words, wave and particle, have very different meanings, and therefore, seemingly cannot describe the same object. 

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last modified 1/5/2001 email Fermilab 
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