Modern Physics - SS1 Physics Past Questions and Answers - page 3

The photoelectric effect refers to the emission of electrons from a metal surface when it is exposed to light. This phenomenon played a crucial role in supporting the particle nature of light and the development of quantum theory. According to the classical wave theory of light, the intensity of light should determine the energy transferred to the electrons, and the emission of electrons should occur regardless of the frequency of light. However, experimental observations showed that the intensity of light did not affect the kinetic energy of emitted electrons, but the frequency of light did.

Einstein's explanation of the photoelectric effect revolutionised our understanding of light. He proposed that light consists of particles called photons, each carrying a discrete amount of energy proportional to its frequency. When a photon interacts with a metal surface, it transfers its energy to an electron. If the energy of the photon is greater than the work function of the metal (the minimum energy required to release an electron), the electron is emitted with kinetic energy equal to the difference between the photon's energy and the work function.

Practical applications of the photoelectric effect include solar cells, where the absorption of photons by a semiconductor material generates an electric current, and photomultiplier tubes, which convert photons into electrical signals for various detection and imaging purposes.