Labs / Physics
Photoelectric Effect
Aim a beam of coloured light at a metal plate and sweep its frequency by dragging across the canvas. Electrons only leap free once each photon carries more energy than the metal's work function — turning the brightness up never helps if the colour is too red. Adjust the intensity, swap metals, and dial in a stopping voltage to measure how fast the electrons come off.
Ephoton 4.96 eVW 2.28 eVKEmax 2.68 eVI 0 e⁻/s
What to try
- Crank the intensity to 100% on red light. Why does a blindingly bright red beam still eject no electrons?
- Slowly raise the frequency on cesium. At what photon energy do the first electrons suddenly appear?
- Switch from cesium to platinum without touching the colour. Where did all the electrons go?
- With electrons flying, raise the stopping voltage. What value just barely stops the fastest ones — and how does that compare to the max kinetic energy?
- Does more intensity change how fast each electron leaves, or only how many leave per second?