If the energy of incident radiation is increased by 25%. The kinetic energy of the photoelectrons emitted from the metal surface increased from 0.6 eV to 0.9 eV. The work function of the metal is :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 0.6 eV
By Einstein's photoelectric equation, the maximum kinetic energy is the photon energy minus the work function \( \phi \).
\( \displaystyle K_{\max} = E - \phi \)
Let the initial photon energy be \( E \). Then the two cases give
\( E - \phi = 0.6\,\mathrm{eV} \)
\( 1.25E - \phi = 0.9\,\mathrm{eV} \)
Subtracting the first equation from the second,
\( 0.25E = 0.3\,\mathrm{eV} \)
\( E = 1.2\,\mathrm{eV} \)
\( \phi = E - 0.6 = 1.2 - 0.6 = 0.6\,\mathrm{eV} \)