Photoelectric Effect

(1) When radiations with certain minimum frequency (v0) strike the surface of a metal, the electrons are ejected from the surface of the metal. This phenomenon is called photoelectric effect and the electrons emitted are called photo-electrons. The current constituted by photoelectrons is known as photoelectric current.

(2) The electrons are ejected only if the radiation striking the surface of the metal has at least a minimum frequency (v0) called Threshold frequency. The minimum potential at which the plate photoelectric current becomes zero is called stopping potential.

(3) The velocity or kinetic energy of the electron ejected depend upon the frequency of the incident radiation and is independent of its intensity.

(4) The number of photoelectrons ejected is proportional to the intensity of incident radiation.

(5) Einstein’s photoelectric effect equation

According to Einstein, Maximum kinetic energy of the ejected electron = absorbed energy – threshold energy

1/2mv2max = hv - hv0 = hc [1/λ - 1/λ0]                    

Where, v0 and λ0 are threshold frequency and threshold wavelength.

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