The kinetic energy of most energetic electrons emitted from a metallic surface is doubled when the wavelength , $\lambda$ of the incident radiation is changed from 400 nm to 310 nm. The work function of the metal is 

• A

  0.9 e.V

• B

  1.7 e.V

• C

  2.2 e.V

• D

  3.1 e.V