In 1900, Max Planck derived the correct form for the intensity spectral distribution function by making some strange (for the time) assumptions. In particular, Planck assumed that electromagnetic radiation can be emitted or absorbed only in discrete packets, called quanta, of energy: formula_2, where "h" is Planck's constant. Planck's assumptions led to the correct form of the spectral distribution functions: formula_3. Albert Einstein (in 1905) and Satyendra Nath Bose (in 1924) solved the problem by postulating that Planck's quanta were real physical particles — what we now call photons, not just a mathematical fiction. They modified statistical mechanics in the style of Boltzmann to an ensemble of photons. Einstein's photon had an energy proportional to its frequency and also explained an unpublished law of Stokes and the photoelectric effect. This published postulate was specifically cited by the Nobel Prize in Physics committee in their decision to award the prize for 1921 to Einstein.