Dual Nature of Radiation and Matter – Notes

Photoelectric Effect
The “Photoelectric effect” is a phenomenon of the emission of electrons by a metal surface after absorbing “light energy”.
The electrons thus emitted are called “photo electrons”.
The history of the photoelectric effect dates back to 1887, when this phenomenon was accidentally discovered by Heinrich Hertz.
Hertz discovered that due to the photoelectric effect, when light fell on a surface, some of the electrons on the surface absorb enough energy from the incident radiation to overcome the attractive force of the positive ions of the material of the surface.
Lenard concluded from his experiment that as soon as ultraviolet radiation falls on a cathode plate, it emits electrons.
Hallwachs concluded from the various observations of his experiment that negatively charged particles are emitted from a zinc plate under the action of ultraviolet light.

Study of Photoelectric Effect
For a given photosensitive material and frequency of incident radiation, photoelectric current is directly proportional to the intensity of incident light.