A photoelectric surface is illuminated successively by monochromatic light of wavelength lambda and lambda2.

A photoelectric surface is illuminated successively by monochromatic light of wavelength lambda  and  lambda2 . 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)