Tuesday, 31 January 2017

How quantum theory explains colours

When Schrodinger developed his famous equation he used it to model the waves of electrons in atoms. He and others found that for any given element only certain waves fitted with his equation, and those waves had particular energy values associated with them.
What was amazing was that the differences between the energies of the waves in an atom exactly match the energies of the photons of light that appeared in the element’s spectrum. Here was an explanation of colour!
It seemed that electrons could jump between energy levels in an atom. An electron in a low energy level could jump to a higher energy by absorbing a photon that had exactly the right energy to make up the difference between the two levels.  Likewise an electron in a higher energy level could drop to a lower one, giving off the energy difference in an emitted photon.

Going back to the spectrum of hydrogen, the energies of the photons that make up different coloured bands of light correspond exactly to the jumps between the energy levels of electrons in a hydrogen atom that are predicted by Schrodinger’s equation.
Imagine how exciting it must have been for Schrodinger to have made calculations using his new equation  to find that they predicted something so fundamental as the colours of elements, something that physics had never been able to explain before.

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