A photoelectric surface is illuminated successively by monochromatic light of wavelength $\lambda$ and $\frac{\lambda }{2}$. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the material is:
($h$ = Planck's constant, $c$ = speed of light)

• A

  $\frac{hc}{\lambda }$
• B

  $\frac{2hc}{\lambda }$
• C

  $\frac{hc}{3\lambda }$
• Correct answer
  D

  $\frac{hc}{2\lambda }$

Hence, the correct answer is option: 'D'.