Photoelectric Effect Simulator (2D)

This 2D simulator draws a lamp facing a metal plate from the side: colored photon dots stream across the gap at a rate set by the intensity slider, while their color and energy are set by the frequency slider. Pick a target metal — cesium, sodium, zinc or platinum — each with its own real work function, and watch what happens when a photon lands on the plate: below the metal's threshold frequency nothing is ejected no matter how bright the beam gets, but the instant frequency crosses that threshold, green electron dots fly off the surface with a kinetic energy that depends only on frequency, exactly as Einstein's 1905 photon explanation predicts. Live readouts track photon energy, work function, threshold frequency, ejection rate, maximum kinetic energy and the stopping voltage needed to halt the fastest electron.