Conclusions:
It is the phenomenon of emission of electrons from the surface of metals, when light radiations (Electromagnetic radiations) of suitable frequency fall on them. The emitted electrons are called photoelectrons and the current so produced is called photoelectric current.
This effect is based on the principle of conservation of energy.
Terms related to photoelectric effect
(i) 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; l0 = Threshold wavelength
Work function is often stated in electron volt W0(eV).
(ii) Threshold frequency (n0) : The minimum frequency of incident radiations required to eject the electron from metal surface is defined as threshold frequency.
If incident frequency n < n0 Þ No photoelectron emission
(iii) Threshold wavelength (&lambda0) : The maximum wavelength of incident radiations required to eject the electrons from a metallic surface is defined as threshold wavelength.
If incident wavelength &lambda > &lambda0 Þ 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. So if an electron in a metal absorbs a photon of energy E (= hn), it uses the energy in the following ways:
(i) Some energy (say W0) is used in making the surface electron free from the metal.
(ii) Rest energy will appear as kinetic energy (K) of the emitted photoelectrons. Hence E = W0 + K This is the Einstein's photoelectric equation
