Coupon Accepted Successfully!


Photo-Electric Effect

The photo-electric effect is the emission of electrons (called photo-electrons) when light strikes a surface. To escape from the surface, the electron must absorb enough energy from the incident radiation to overcome the attraction of positive ions in the material of the surface.
The photo-electric effect was first observed by Heinrich Hertz and it was investigated in detail by Whilelm Hallwachs and Philipp Lenard.
The photo-electric effect is based on the principle of conservation of energy.

Work function (or threshold energy) (W0)

The minimum energy of incident radiation, required to eject the electrons from metallic surface is defined as work function of that surface.
v0 = threshold frequency; λ0 = threshold wavelength.
Work function in electron volt W0(eV)

Threshold frequency (v0)

The minimum frequency of incident radiations required to eject the electron from metal surface is defined as threshold frequency.
If incident frequency v < v0 No photoelectron emission
For most metals, the threshold frequency is in the ultraviolet spectrum (corresponding to wavelengths between 200 and 300 nm), but for potassium and cesium oxides it is in the visible spectrum (λ between 400 and 700 nm).

Threshold wavelength (λ0)

The maximum wavelength of incident radiations required to eject the electrons from a metallic surface is defined as threshold wavelength.
If incident wavelength λ > λ0 No photoelectron emission

Einstein’s photoelectric equation

According to Einstein, photoelectric effect is the result of one to one inelastic collision between photon and electron in which photon is completely absorbed
Fig. 4
Einstein’s photoelectric equation is E = W0 + Kmax, where 99820.png maximum kinetic energy of emitted electrons.

Test Your Skills Now!
Take a Quiz now
Reviewer Name