22.2.1—Photoelectrons may be emitted from a metal surface when it is illuminated by

The photoelectric effect is emission of electrons from a metal when incident photons have enough energy to overcome the surface work function.

Increasing intensity above threshold increases the number of emitted electrons, while frequency controls each photon’s energy and maximum electron speed.

Dim ultraviolet light can eject electrons while bright red light may not if red photon energy is below threshold.

Photoemission is not caused by accumulating energy over time from sub-threshold photons in the simple model.