Photoelectric Effect — iLearnSTEM Labs

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labs.ilearnstem.ca — Virtual Science Laboratories

Ontario Curriculum · Grades 9–12Beta

Photoelectric Effectat the cutoff

metal Sodium · φ 2.36 eVλ 400 nmhf 3.10 eVI 0.0 nAV 0.00 V

Every electron is being turned back mid-gap — watch the cyan streaks stall and return. eV₀ = hf − φ at exactly this voltage.

Physics Lab 11 · Photoelectric Effect — KE_max = hf − φ, one photon at a time · the needle lags like a real electrometer · drag to orbit, scroll to zoom

Lamp

Wavelength400 nm

Colour IS energy: hf = 3.10 eV at this setting — violet photons carry nearly twice what red ones do.

Intensity50%

Intensity is photons per second — it sets how MANY electrons flow, never how hard each one is kicked.

Photocell

Cathode metalSodium · φ 2.36 eV

The work function φ is the entry fee: photons with hf < φ eject nothing, at any brightness.

Retarding voltage0.00 V

The anode is held negative to push electrons back. The voltage that just kills the current IS the kinetic energy per electron: eV₀ = KE_max.

What the bench is doing

The meter has just died — this is the cutoff. Record it while the needle is settled.