<P> The concept of quantization of radiation was discovered in 1900 by Max Planck, who had been trying to understand the emission of radiation from heated objects, known as black - body radiation . By assuming that energy can be absorbed or released only in tiny, differential, discrete packets (which he called "bundles", or "energy elements"), Planck accounted for certain objects changing colour when heated . On December 14, 1900, Planck reported his findings to the German Physical Society, and introduced the idea of quantization for the first time as a part of his research on black - body radiation . As a result of his experiments, Planck deduced the numerical value of h, known as the Planck constant, and reported more precise values for the unit of electrical charge and the Avogadro--Loschmidt number, the number of real molecules in a mole, to the German Physical Society . After his theory was validated, Planck was awarded the Nobel Prize in Physics for his discovery in 1918 . </P> <P> While quantization was first discovered in electromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons . In the attempt to bring theory into agreement with experiment, Max Planck postulated that electromagnetic energy is absorbed or emitted in discrete packets, or quanta . </P>

Definite value of energy possessed by aquantum of radiation is called