Dual Nature of Matter and Radiation

Electron Emission and Experimental Study of Photoelectric Effect


  • Photoelectric effect supports the quantum theory of light.
  • When light of suitable frequency with certain wavelength falls on some alkali metals, electrons are released from the metal. This effect is known as PHOTO ELECTRIC EFFECT.
  • Photoelectric effect is interaction of energy with matter
  • THRESHOLD FREQUENCY (ν0), is the minimum frequency of the incident radiation below which no photoelectric emission takes place.
  • THRESHOLD WAVE LENGTH (λ0), is the maximum wave length of the incident radiation above which no photo electric emission takes place.
  • WORK FUNCTION (W) is the minimum energy required to remove a free electron from the metal \tt W=h\nu_{0}=\frac{hc}{\lambda_{0}}
  • The minimum retarding potential to be applied to the collector to just stop the electrons of maximum K.E reaching the anode is called STOPPING POTENTIAL
  • The maximum K.E. emitted from of the electron is equal to the product of stopping potential, Vs and electron charge, e. kmax = eVs
  • The stopping potential, (Vs) depends on
    (a) nature of the metal or work function
    (b) frequency or wavelength of the incident radiation
  • Vs stopping potential is independent of intensity of the incident radiation.

View the Topic in this video From 00:08 To 19:03

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1. The most energetic photoelectrons, with the maximum kinetic energy (Kmax), so that Kmax = e V0

2. Photon Counts Emitted by a Source Per Second

E = hv = \frac{hc}{\lambda}