Planck's law

Max Planck introduced Planck's law in 1900, which describes the spectral radiance of electromagnetic radiation emitted by a black body. The law fundamentally relies on the concept of energy quantization, proposing that energy is emitted in discrete packets called "quanta".

Planck's law solved the "ultraviolet catastrophe," a flaw in classical physics that incorrectly predicted a black body would emit infinite energy at high frequencies. By introducing quantized energy emission, Planck's mathematical model correctly matched the observed experimental data.

Planck's law explains the principle behind thermal radiation, which is why heated objects change color as they get hotter. For instance, it mathematically defines why a piece of iron glows dull red at lower temperatures and turns bright white as its temperature increases.

Planck's law is widely considered the foundational breakthrough that sparked the entire field of quantum mechanics. The mathematical constant he formulated to solve the black-body problem, known as Planck's constant (h), remains a fundamental pillar of quantum physics today.