What is the work function of the metal if the light of wavelength 4000 generates photoelectrons of velocity 6 × 10^5 ms^-1 from it? (Mass of electron…

What is the work function of the metal if the light of wavelength $\displaystyle 4000 \AA$ generates photoelectrons of velocity $\displaystyle 6 \times 10^5 \mathrm{~ms}^{-1}$ from it ? (Mass of electron $\displaystyle =9 \times 10^{-31} \mathrm{~kg}$ Velocity of light $\displaystyle =3 \times 10^8 \mathrm{~ms}^{-1}$ Planck's constant $\displaystyle =6.626 \times 10^{-34} \mathrm{Js}$ Charge of electron $\displaystyle =1.6 \times 10^{-19} \mathrm{JeV}^{-1}$ )