Introduction to Photoelectric Effect

Photoelectric effect

When light or electromagnetic radiation falls on a metal surface, electrons are emitted from it. The process of emission of electrons from a metallic surface by the incidence of light (photons) is known as photoelectric effect. The emitted electrons are called photoelectrons. The picture below illustrates the photoelectric effect.

Emission of electrons from metallic surface

Some important terms:

Threshold frequency (fo): The minimum frequency below which photoelectric emission is not possible is known as threshold frequency. The value of threshold frequency is different for different metals.

hfo = ϕ   [Where h=Planck’s constant]

or, fo =ϕ/h

Threshold wavelength (λo): The maximum wavelength of light which can eject photoelectrons from a surface is called threshold wavelength. It is the wavelength corresponding to threshold frequency.

λo = c/fo[Where c =velocity of light]

Work function (ϕ): The minimum energy required to eject an electron from the surface is called threshold energy or work function. It is denoted by ϕ and measured in eV. Its value depends on the nature of metal, its purity and the condition of the surface.

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