Max Planck provided the foundation for the quantum theory with the law of rays
(Strahlungsgesetz). According to classical physics radiation occurs in undefined small
portions. According to quantum physics radiation occurs only as a multiple of the number
being the frequency of the radiation and h being a natural constant, the so-called
Plancks (quantum) constant: Its value is 6,63·10-34Js,
its dimension (energy · time) is called effect.In 1905,
Albert Einstein put into words the light quantum hypothesis, which states that light of
the frequency n consists of parts, called photons, with energy E =h·n .
idea that light is made up of parts was in stark opposition to the theory of waves and
raised the question if these two ideas could be somehow reconciled.