Question

Light of wavelength 2000 Å falls on a metal surface of work function 4.2 eV.

What is the kinetic energy (in eV) of the fastest electrons emitted from the surface?

Answer 1

λ = 2000 Å = (2000 × 10^-10)m

W_o = 4.2eV

h = 6.63 × 10^-34 JS

Using Einstein's photoelectric equation
K. E. = (6.2 – 4.2) eV = 2.0 eV