Question

what is planks quantum theory

Answer 1

Plank's quantum hypothesis/theory states that
Energy can only be emitted and absorbed in bundles called quanta.

Hope this helps.

Answer 2

Here is your answer....

Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. The law is named after Max Planck, who proposed it in 1900. It is a pioneering result of modern physicsand quantum theory.

Hope it helps you.