English 
The photoelectric effect is that under the irradiation of electromagnetic waves (limit frequency threshold frequency) higher than a certain frequency, electrons inside certain substances absorb energy and escape to form an electric current (photogenerated electricity).
The phenomenon of electro-optics was discovered by Hertz in 1887, and the now widely accepted explanation is that of Einstein (listen to Einstein's real voice).
According to the particle theory, light is composed of discrete photons. When a photon irradiates a photosensitive substance, the energy can be absorbed by an electron in the substance. After the electron absorbs energy, the kinetic energy increases; if the kinetic energy increases enough to overcome the gravitational pull of the nucleus on it, it becomes a flow of photoelectrons. In unit time, the greater the number of incident photons, the more photoelectrons that escape, and the stronger the photocurrent. This phenomenon of automatic discharge from light energy into electrical energy is called the photoelectric effect.
