It was Philipp Lenard, an assistant of Hertz, who performed the earliest, definitive studies of the photoelectric effect. It meant rebuilding a large portion of physics from the ground up. Repairing this tear in theory required more than just a patch. When it interacted with electrons, light just didn't behave like it was supposed to. Subsequent investigations into the photoelectric effect yielded results that did not fit with the classical theory of electromagnetic radiation. The era of modern physics is one of completely unexpected and inexplicable discoveries, however.
All forms of electromagnetic radiation transport energy and it is quite easy to imagine this energy being used to push tiny particles of negative charge free from the surface of a metal where they are not all that strongly confined in the first place. While this is interesting, it is hardly amazing. Thomson showed that this increased sensitivity was the result of light pushing on electrons - a particle that he discovered in 1897.
Hertz found that he could increase the sensitivity of his spark gap device by illuminating it with visible or ultraviolet light. The air gap would often have to be smaller than a millimeter for a the receiver to reliably reproduce the spark of the transmitter.
Compared to later radio devices, the spark gap generator was notoriously difficult to work with. In these experiments, sparks generated between two small metal spheres in a transmitter induce sparks that jump between between two different metal spheres in a receiver. The photoelectric effect was first observed in 1887 by Heinrich Hertz during experiments with a spark gap generator (the earliest device that could be called a radio). All electrons are identical to one another in mass, charge, spin, and magnetic moment. This process is called the photoelectric effect (or photoelectric emission or photoemission), a material that can exhibit this phenomenon is said to be photoemissive, and the ejected electrons are called photoelectrons but there is nothing that would distinguish them from other electrons. Under the right circumstances light can be used to push electrons, freeing them from the surface of a solid.