Define the following with reference to photoelectric effect : b Stopping potential V s

The negative potential at which the photoelectric current becomes zero is called stopping potential or cut ‐ off potential. It is the negative potential of the anode for which even the fasts moving electrons cannot reach it. It is a measure of the maximum kinetic energy of the electrons emitted as a result of the photoelectric effect.

Define the following with reference to photoelectric effect : a Threshold frequency f o

The lowest frequency of light which can emit photoelectrons from a metal surface is called the threshold frequency, f 0 of that material. So it is the minimum frequency below which photoelectric effect does not take place. It is a characteristic of electromagnetic radiation ( light in case of photoelectric emission ) and not metal.

With reference to photoelectric effect, define threshold wavelength.

The work function of a metal is the minimum energy required to eject an electron from the surface of the metal, without imparting any kinetic energy to the electron. The energy of incident photon is given by E = hν = h . c λ where ν , λ and c are the frequency, wavelength and the speed of light photon. It is clear from the above, to eject a photoelectron from a metal surface there is a maximum limit of the wave length of the incident light which should not to be exceeded.This is called threshold wave length.