Photoelectric Effect Summary

Experimental Observation	Wave Model Explanation	Photon Model Explanation
The photocurrent is produced nearly instantaneously after light strikes the metal surface.	The photocurrent is produced only when sufficient energy has been deposited over the metal surface to liberate electrons. Thus, for low intensity light, long times would be required to build up enough energy to liberate electrons Wave model fails.	One photon interacts with one electron giving up its energy and emitting the electron nearly instantaneously.
The photocurrent is directly proportional to the intensity of the light striking the metal surface.	Intensity is the amount of energy per unit area per unit time falling on the metal surface. Higher intensity means that more energy is available to liberate more electrons.	Intensity is the number of photons per unit area per unit time falling on the metal surface. Higher intensity means that there are more photons available to liberate more electrons in one-on-one interactions.
The maximum kinetic energy of the photoelectrons (and the stopping potential) is directly proportional to the frequency of the light striking the metal surface and independent of its intensity.	No explanation. Wave model fails.	A single photon of energy, hf, strikes an electron overcoming the energy by which the electron is held to the metal surface, and gives the electron its remaining energy in the form of kinetic energy. The maximum kinetic energy is produced when a photon strikes an electron that is held with the minimum energy to the metal surface (work function).
There is a threshold frequency below which no photocurrent is produced no matter how great the intensity of the light striking the metal surface.	No explanation. Wave model fails.	If the energy of the photon, hf, is less than the minimum binding energy of an electron to the metal surface (work function), no electron can be emitted.