Three clean metallic surfaces A, B and C have work functions

PHYSICS · Multi-part · CBSE · Physics · Dual Nature of Radiation and Matter · Dual Nature of Radiation and Matter

Problem

\phi_A = 2.0\,\text{eV}

\phi_B = 3.0\,\text{eV}

and

\phi_C = 4.5\,\text{eV}

, respectively. Monochromatic light of wavelength

400\,\text{nm}

falls normally on each surface with the same intensity. (Take

h=6.63\times10^{-34}\,\text{J\,s}

c=3.0\times10^{8}\,\text{m\,s}^{-1}

e=1.6\times10^{-19}\,\text{C}

and

1\,\text{eV}=1.6\times10^{-19}\,\text{J}

.) (i) Calculate the energy of a photon of the incident light in electron-volt. (ii) For each metal, state whether photo-emission occurs. Show your comparison clearly. (iii) For those metals that do emit electrons, calculate the stopping potential required to just halt the most energetic photo-electrons. (iv) Arrange the emitting metals in descending order of their stopping potentials and hence of the maximum kinetic energies of their photo-electrons.

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