I may have written a previous post dedicated to Quantum Mechanics but I wanted to take this opportunity and write more about Max Planck since his work is the actual basis of quantum theory (interesting fact: he received his degrees from the University of Berlin and University of Munich and he also won a Nobel Prize for Physics in 1918!)
In order to understand the spectral-energy distribution of radiation from a blackbody (physical body that takes in all electromagnetic radiation, no matter the frequency or angle of incidence) Planck believed that the source of radiation were made up of atoms in a state of oscillation (moving back and forth or period motion) and that vibrational energy of each oscillator (which can take in or give off energy only in quantities which are multiples of Planck’s constant times the frequency of the oscillator) may have any of a series of discrete values but never any value between.
When an oscillator changes from E1 (state of energy) to a lower state E2, the amount of energy E1 − E2 (or quantum of radiation) is equal to the product of the frequency of radiation (frequency in physics meaning number of waves that go through a fixed point in unit time and also number of cycles throughout one unit of time in periodic notion) which is now formulized as Planck’s constant that he created from blackbody radiation information, for instance E1 − E2 = hν.
The Stefan-Boltzmann law discusses the blackbody emissive power (known as Eb) which is the sum of radiation from all wavelengths. Planck’s law explains the range of blackbody radiation (amount of radiation from a surface at a specific wavelength based on the surface temperature, condition of the surface and material of the body) which depends on the object’s temperature and relates to the blackbody emissive power of Ebλ (λ meaning wavelength). Planck’s law has been written using modern physics and quantum theory and his hypothesis is based upon the idea that energy is emitted in “discrete quanta”. It’s also important to point out that Wien’s displacement law gives the wavelength at which the Planck law has the most/maximum intensity. You can see this happen using the equation of where h is Planck’s constant, c is the speed of light, k is Boltzmann’s constant and T is the temperature.