Question

Explain the photoelectric effect. Write the Einstein’s equation for the photoelectric effect and name all the terms of the equation.

Answer 1

Photoelectric effect

When light falls on a metal surface, electrons emits from the surface. This phenomenon is called photoelectric effect. But this emission of light will not happen all times. For example, the light of any frequency falling on the metal surface cannot emit the electron. The electron will emit for light with some frequency which is greater than a cutoff frequency. This frequency is different for different metal also. This phenomenon is exhibiting the particle property of the light. Here light is acting as a packet of energy(which is called photons) and these photons collide with the free moving electrons in the metal surface. During the collision, photons transfer it's full energy to the electron. One photon transfer its full energy to one electron only at a time. If this energy is sufficient for the electron to overcome the bonding with metal, then the electron will emit from the surface. This is the explanation on this phenomenon given by Einstein. He explain this entire scenario, in an equation called  Einstein’s equation for the photoelectric effect. The equation is,

here

is the energy of the photon which is transferred to the electron. The minimum amount of energy e required to overcome the binding with the atom is   which is called work function. This is the particularity of the metal. For different metals, work function is different. The remaining energy is will be used as KE for the emitted electrons. So if the energy of the photon, less than the work function, the e will not emits from the surface. So minimum frequency which the incoming light should have to occur the photoelectric effect is ,