In 1887, H Hertz performed a very interesting experiment in which electrons (or electric current) were ejected when certain metals (for example potassium, rubidium, cesium etc.) were exposed to a beam of light as the phenomenon is called Photoelectric effect.
The result observed in this experiment were: (i). The electron are ejected from the metal surface as soon as the beam of light strikes the surface, i.e., there is no time lag between the striking of light beam and the ejection of light beam and the ejection of electron from the metal surface.
(ii). The number of electron ejected is proportional to the intensity or brightness of light.
(iii). For each metal, there is a characteristic minimum frequency, (also known as threshold frequency) below which photoelectric effect is not observed. At a frequency the ejected electrons come out with certain kinetic energy.
The kinetic energy of these electrons increases with the increase of frequency of the light used.
All the above result could not be explained on the basis of laws of classical content of the bases of laws of classical content of the beam of light depends upon number of electrons ejected and kinetic energy associated with them should depend observed that thought the number of electron.
