What is the external photoelectric effect and the internal photoelectric effect?
When light shines on a certain metal surface, part of the photons are reflected by the surface, and the other part of the photons are absorbed by the metal. The absorbed photons give their energy to the metal lattice and free electrons, the amplitude of the lattice vibration increases, and the disordered movement of free electrons accelerates rapidly. If the energy of the photon is large, equal to or greater than the binding force of the metal, the electrons can escape the metal surface. This phenomenon is called the external photoelectric effect. If the energy of the photon is less than the binding force of the metal, this part of the energy will eventually be used to heat the metal. Photoelectric tubes, photomultiplier tubes, etc. are photoelectric elements made based on the external photoelectric effect.
When light shines on certain semiconductor materials between a certain metal and an insulator, the number of free electron-hole pairs inside the semiconductor will increase rapidly. This is because the energy of some photons is sufficient to free the electrons from the bondage of atoms. Exciting electrons from the full band to the conduction band, this phenomenon is called the internal photoelectric effect.
The above is the introduction of the external photoelectric effect and the internal photoelectric effect.
What are the characteristics of light? You can learn more.
