Photoelectric effect is the emission of electrons from a substance when electromagnetic radiations fall on it. For instance, when light falls on a metal plate, electrons are ejected.

Light with energy above a particular point frees electrons from the surface of the solid metal. Each photon (particle of light) collides with an electron and uses some of its energy to remove the electron. Photon’s remaining energy transfers to the free negative charge which is called a photoelectron. This was a discovery that revolutionized modern physics as it clarified many doubts regarding the nature of light.

The photoelectric effect proposed by Einstein in 1905 remains valuable in various areas of research such as material science and astrophysics. It is also the basis of many useful devices. The ‘electric eye’ door openers, light metres used in photography, solar panels and Photostat copying are all applications of the photoelectric effect.

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