The Photoelectric Effect: Einstein’s Nobel-Winning Discovery

The photoelectric effect is when light shining on a metal surface ejects electrons.
Classical physics couldn’t explain why light sometimes failed to free electrons.
In 1905, Einstein proposed that light comes in energy packets called photons.
He showed that each photon’s energy depends on its frequency, not its brightness.
If a photon’s energy is too low, no electrons are released—no matter the intensity.
Brighter light means more photons, but only higher frequency frees electrons.
This proved that light has both wave and particle properties.
Einstein’s explanation laid the foundation for quantum mechanics.
The effect is used today in solar panels, night vision, and light sensors.
Einstein won the 1921 Nobel Prize in Physics for this groundbreaking discovery.