How did Einstein come up with the solution of The Photoelectric Effect?

This video delves into the photoelectric effect, discussing how Einstein’s ideas challenged prevailing scientific beliefs. Initially, Einstein asserted that light’s particulate nature was intrinsic, not just a description of its interactions. Planck initially resisted this notion, believing light quanta were only relevant during absorption or emission, not in a vacuum. Despite their disagreement, Planck later recommended Einstein for a prestigious position, acknowledging his merit despite reservations about some of his ideas.