Q. Light of wavelength $4000\mathring{\mathrm{A}}$ is incident on a metal surface. The maximum kinetic energy of emitted photoelectron is 2 eV. What is the work function of the metal surface ?
A) 4 eV
B) 1 eV
C) 2 eV
D) 6 eV
Explanation
(b) According to Einstein’s photoelectric equation the work function of metal is given by
∴ ϕ= hc/λ-KE$_{m}$
= $\frac{6.6 \times 10^{- 34} \times 3 \times 10^{8}}{4000 \times 10^{- 10}} - 2eV$
$= \ 4.95 \times 10^{- 19} - 2\ eV$
$= \ \frac{4.95 \times 10^{- 19}}{1.6 \times 10^{- 19}} - 2\ eV$
= 3 eV-2 eV = 1 eV
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.