Induction coils with spark gaps were the first devices to suggest its existence. When the receiving coil in an 1887 experiment was enclosed in a dark case, the observed spark was always smaller. The aforementioned work by Hertz was followed by contributions in the area from 
Induction coils with spark gaps were the first devices to suggest its existence. When the receiving coil in an 1887 experiment was enclosed in a dark case, the observed spark was always smaller. The aforementioned work by Hertz was followed by contributions in the area from Thomson and Lenard. Lenard found that it was independent of the ultraviolet light's intensity, but it took until the article On a Heuristic Point of View about the Creation and Conversion of Light for the concept to be widely diffused. For 10 points, the work function is associated with this effect, whose discovery won the 1905 Nobel Prize for Physics for Albert Einstein.
Induction coils with spark gaps were the first devices to suggest its existence.
{photoelectric} effect