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MotionLab
The experiment that proved light comes in packets (photons) and earned Einstein his Nobel Prize.
Classical physics predicted that brighter light (any frequency) should eventually eject electrons. Instead, experiments showed that only light above a threshold frequency works, no matter how bright — Einstein explained this by proposing that light energy comes in discrete packets (photons), each carrying E = hf.
Each metal has a characteristic work function (φ) — the minimum energy needed to free an electron from the surface. If the photon's energy (hf) exceeds φ, the leftover energy becomes the electron's kinetic energy; if not, no electron escapes regardless of light intensity.
Kinetic energy (eV)
1.836
KE = hf − φ
What you entered
Photon energy E = hf
6.626e-34 × 1.000e+15= 4.1357 eVKE = hf − φ
4.1357 − 2.3= 1.8357 eVElectron emitted?
E > φ?= YesResult
Kinetic energy (eV): 1.836
A photon at 1.00e+15 Hz (4.136 eV) ejects an electron with 1.836 eV of kinetic energy (work function = 2.3 eV).