Photoelectric Effect
The emission of electrons from a metal surface when light of frequency above a threshold value shines upon it.
Governing formula
K_max = h ν - Φ = e V_stopping
SI unit
eV or Joules
In depth
Albert Einstein explained the effect in 1905 by proposing light consists of localized energy packets (photons). Electron emission depends on photon frequency ν (energy E=hν), not light intensity, proving light's particle nature.
Examples in the real world
Solar photovoltaic panels generating electricity from sunlight, and photomultiplier tubes detecting faint light.