UV radiation of 6.2 eV falls on aluminium surface of work function 4.2 eV. The stopping potential for the surface is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 2\,\mathrm{V} \)
By Einstein's photoelectric equation the maximum kinetic energy of a photoelectron is the photon energy minus the work function, and the stopping potential \( V_0 \) is the retarding potential that just stops these electrons, \( eV_0 = K_{\max} \).
\( eV_0 = h\nu - \phi_0 \)
\( eV_0 = 6.2\,\mathrm{eV} - 4.2\,\mathrm{eV} = 2.0\,\mathrm{eV} \)
\( V_0 = 2\,\mathrm{V} \)