The Photoelectric Effect: When Light Knocks Out Electrons

The photoelectric effect happens when light shining on a material ejects electrons.
Classical physics predicted intensity mattered, but experiments showed frequency was key.
Albert Einstein explained it in 1905 by introducing the idea of photons.
Photons are particles of light, each carrying a discrete packet of energy.
Only photons above a threshold frequency can knock out electrons.
Brighter light with too-low frequency won’t eject any electrons at all.
The effect proved light acts like both a wave and a particle.
It provided crucial evidence for the new science of quantum mechanics.
Solar panels use the photoelectric effect to convert sunlight into electricity.
Einstein won the 1921 Nobel Prize in Physics for explaining this phenomenon.