Planck postulated that the energy of oscillators in a blackbody is quantized by

(1)

where n = 1, 2, 3, ..., h is Planck's constant, and is the frequency, and used this postulate in his derivation of the Planck law of blackbody radiation. In fact, electromagnetic radiation is itself quantized, coming in packets known as photons and having energy

(2)

In the other hand, the energy of state n of quantum mechanical simple harmonic oscillator is actually given by the slightly modified form

(3)

Photon, Planck Law, Simple Harmonic Oscillator--Quantum Mechanical