>>11254559You would expect a more intense radiation source to eject electrons from the material at greater velocities. In fact this does not happen: more electrons are ejected, but they are as energetic as before. Only by varying the frequency of the radiation source can you give the electrons greater velocity once the work function is overcome.
The interpretation, which is consistent with every experiment done since, is that the intensity of a radiation source is proportional to the number of photons, and the energy of those photons is fixed. If in one event, an electron only has time to absorb one photon's worth of energy before being ejected from the material, then it makes sense that having more photons does not make the electron have a greater energy after it has exited. But there are more photons when the radiation is more intense, so more electrons can be ejected from the material by absorbing a single one. The energy they get once ejected is just the frequency of the photon (times a constant called Planck's constant), minus the work function.
But the process of absorbing and emitting this radiation is one completely consistent with classical physics. No quantum mechanics is needed to explain that effect.
