Light of wavelength $\lambda$ strikes a photo electric surface and electrons are ejected with maximum kinetic energy K. If K is to be increased to twice its original value, the wavelength must be changed to ${\lambda }^{\text{'}}.$ $If\lambda =6200\stackrel{o}{A}and{\lambda }^{\text{'}}=5000\stackrel{o}{A},$ Then value of k is

• A

  1.26 eV

• B

  0.86 eV

• C

  0.48 eV

• D

  1.62 eV