Photoelectric Effect
Also known as work function equation · einstein photoelectric
Worked example: Sodium phi = 2.28 eV, 3.1 eV photon → KE = 0.82 eV — press Try an example to run it live, then adjust anything.
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Photoelectric Effect explained
Shine light on a metal and electrons pop out — but only if the frequency is high enough, no matter how bright the beam. Einstein's 1905 explanation (his Nobel prize, not relativity) is bookkeeping with photons: one photon hands its hf to one electron, which spends φ escaping the surface and keeps the rest as kinetic energy. Below the threshold frequency f₀ = φ/h nothing emerges at all.
For cesium, φ ≈ 2.1 eV, so even dim blue light ejects electrons while intense red light does nothing — the observation that classical wave theory could never explain, and the operating principle of every photomultiplier tube.
Photoelectric Effect formula
- = Work function (J)
- = Photon energy (J)
- = Max kinetic energy (J)
Missing one of these? Work it out first, then come back
- Work function — Work (W = Fd cos θ), Power (P = W/t)
- Photon energy — Photon Energy (E = hf), Photon Energy from Wavelength (E = hc/λ)
- Max kinetic energy — Kinetic Energy, Rotational Kinetic Energy