“Common sense is that layer of prejudices we acquire before we are 16.”
– Albert Einstein
The physical world that was opening up in 1900 was revealed and seen in a radical light. Max Planck’s bold hypothesis that light was emitted in bundles or quanta of energy where each quantum’s energy is determined by the frequency was completely without precedence. Planck tried for a number of years to fit his quantum hypothesis into the fabric of classical physics but failed.
In 1905, Albert Einstein published a paper proposing that light was not only emitted in integral units or bundles of energy but it was also absorbed in such bundles – bundles that came to be known as photons. Again the energy of absorption was equal to the mysterious, h, Planck’s constant multiplied by the light’s frequency, f. Indeed this is the same equation of Max Planck where the quantum of action, h, was introduced for the first time in 1095: E= hf. This is the single equation that changed the world of physics.
Nothing could have been more contrary to the prevailing ideas at that time concerning the transfer of energy of a wave. Since light is in the form of waves, it has to got transfer its energy and be absorbed through its intensity and not by units of its frequency. Einstein in this 1905 paper also provided an explanation for a well-known phenomenon known as photoelectric effect which is associated with the absorption and emission of electromagnetic radiation by matter. It was this work that earned Einstein in 1921 the Nobel Prize in physics not his special theory of relativity which was also published that same year.
The Rutherford-type model of the atom proposed by Niels Bohr in 1913 was an extraordinary success in accounting for the spectrum, stability and other aspects of the hydrogen atom. Its success hinged on the Einstein-Planck quantum relation. However Bohr’s theory failed when applied to helium and other atoms. Plus the fact that the theory contained inconsistencies that could not been resolved.