Physics

Contradictions of classical physics to the photoelectric effect


Of the items listed in the previous topic, the only one that conforms to classical electromagnetic theory is that if we set the frequency and ddp, the electric current will be directly proportional to the intensity of the incident light.

The item that talks about the existence of a cutoff frequency to which electrons start to emit was not even predicted by the classical theory, so it was conceived based on experimental results only.

As for the results predicted by the classical wave theory, the light energy should be evenly distributed over the wavefront, that is, the incident energy would be evenly distributed over the metallic surface of the emitter. Thus, if the incident light were weak, there should be a considerable time lag between the instant light begins to fall on the surface and the ejection of the electron.

During this interval, the electron would absorb energy from the wavefront until it could accumulate enough to be ejected from the plate.

The classical theory also states that the electric current is proportional to the intensity of the emitting light. This means that if we fix the intensity of the incident light, the current will also be fixed without decaying. In addition, the kinetic energy of the electrons is proportional to the radiation intensity, so that each intensity corresponds to a certain kinetic energy value and a respective shear potential, which was not observed in the experiments.

Finally, the photoelectric effect should occur at any light frequency, provided it is sufficiently intense to provide the energy required for electron ejection.